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Revision 1.110 by root, Thu Jun 20 22:44:59 2019 UTC vs.
Revision 1.126 by root, Sat Jun 3 08:53:03 2023 UTC

1.\" Automatically generated by Pod::Man 4.11 (Pod::Simple 3.35) 1.\" Automatically generated by Pod::Man 4.14 (Pod::Simple 3.43)
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132.rm #[ #] #H #V #F C 132.rm #[ #] #H #V #F C
133.\" ======================================================================== 133.\" ========================================================================
134.\" 134.\"
135.IX Title "LIBEV 3" 135.IX Title "LIBEV 3"
136.TH LIBEV 3 "2019-06-20" "libev-4.25" "libev - high performance full featured event loop" 136.TH LIBEV 3 "2023-05-15" "libev-4.33" "libev - high performance full featured event loop"
137.\" For nroff, turn off justification. Always turn off hyphenation; it makes 137.\" For nroff, turn off justification. Always turn off hyphenation; it makes
138.\" way too many mistakes in technical documents. 138.\" way too many mistakes in technical documents.
139.if n .ad l 139.if n .ad l
140.nh 140.nh
141.SH "NAME" 141.SH "NAME"
… …
240watchers\fR, which are relatively small C structures you initialise with the 240watchers\fR, which are relatively small C structures you initialise with the
241details of the event, and then hand it over to libev by \fIstarting\fR the 241details of the event, and then hand it over to libev by \fIstarting\fR the
242watcher. 242watcher.
243.SS "\s-1FEATURES\s0" 243.SS "\s-1FEATURES\s0"
244.IX Subsection "FEATURES" 244.IX Subsection "FEATURES"
245Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the 245Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific aio and \f(CW\*(C`epoll\*(C'\fR
246BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms 246interfaces, the BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port
247for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface 247mechanisms for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR
248(for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner 248interface (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner
249inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative 249inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative
250timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling 250timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling
251(\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status 251(\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status
252change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event 252change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event
253loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and 253loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and
… …
291When libev detects a usage error such as a negative timer interval, then 291When libev detects a usage error such as a negative timer interval, then
292it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism, 292it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism,
293so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in 293so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in
294the libev caller and need to be fixed there. 294the libev caller and need to be fixed there.
295.PP 295.PP
296Via the \f(CW\*(C`EV_FREQUENT\*(C'\fR macro you can compile in and/or enable extensive
297consistency checking code inside libev that can be used to check for
298internal inconsistencies, suually caused by application bugs.
299.PP
296Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has 300Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions. These do not
297extensive consistency checking code. These do not trigger under normal
298circumstances, as they indicate either a bug in libev or worse. 301trigger under normal circumstances, as they indicate either a bug in libev
302or worse.
299.SH "GLOBAL FUNCTIONS" 303.SH "GLOBAL FUNCTIONS"
300.IX Header "GLOBAL FUNCTIONS" 304.IX Header "GLOBAL FUNCTIONS"
301These functions can be called anytime, even before initialising the 305These functions can be called anytime, even before initialising the
302library in any way. 306library in any way.
303.IP "ev_tstamp ev_time ()" 4 307.IP "ev_tstamp ev_time ()" 4
… …
602want to handle signals only in specific threads and want to avoid libev 606want to handle signals only in specific threads and want to avoid libev
603unblocking the signals. 607unblocking the signals.
604.Sp 608.Sp
605It's also required by \s-1POSIX\s0 in a threaded program, as libev calls 609It's also required by \s-1POSIX\s0 in a threaded program, as libev calls
606\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified. 610\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified.
611.ie n .IP """EVFLAG_NOTIMERFD""" 4
612.el .IP "\f(CWEVFLAG_NOTIMERFD\fR" 4
613.IX Item "EVFLAG_NOTIMERFD"
614When this flag is specified, the libev will avoid using a \f(CW\*(C`timerfd\*(C'\fR to
615detect time jumps. It will still be able to detect time jumps, but takes
616longer and has a lower accuracy in doing so, but saves a file descriptor
617per loop.
607.Sp 618.Sp
608This flag's behaviour will become the default in future versions of libev. 619The current implementation only tries to use a \f(CW\*(C`timerfd\*(C'\fR when the first
620\&\f(CW\*(C`ev_periodic\*(C'\fR watcher is started and falls back on other methods if it
621cannot be created, but this behaviour might change in the future.
609.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 622.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
610.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 623.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
611.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 624.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
612This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 625This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
613libev tries to roll its own fd_set with no limits on the number of fds, 626libev tries to roll its own fd_set with no limits on the number of fds,
… …
638This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and 651This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
639\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. 652\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
640.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 653.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
641.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 654.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
642.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 655.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
643Use the linux-specific \fBepoll\fR\|(7) interface (for both pre\- and post\-2.6.9 656Use the Linux-specific \fBepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
644kernels). 657kernels).
645.Sp 658.Sp
646For few fds, this backend is a bit little slower than poll and select, but 659For few fds, this backend is a bit little slower than poll and select, but
647it scales phenomenally better. While poll and select usually scale like 660it scales phenomenally better. While poll and select usually scale like
648O(total_fds) where total_fds is the total number of fds (or the highest 661O(total_fds) where total_fds is the total number of fds (or the highest
… …
694All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or 707All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or
695faster than epoll for maybe up to a hundred file descriptors, depending on 708faster than epoll for maybe up to a hundred file descriptors, depending on
696the usage. So sad. 709the usage. So sad.
697.Sp 710.Sp
698While nominally embeddable in other event loops, this feature is broken in 711While nominally embeddable in other event loops, this feature is broken in
699all kernel versions tested so far. 712a lot of kernel revisions, but probably(!) works in current versions.
713.Sp
714This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
715\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
716.ie n .IP """EVBACKEND_LINUXAIO"" (value 64, Linux)" 4
717.el .IP "\f(CWEVBACKEND_LINUXAIO\fR (value 64, Linux)" 4
718.IX Item "EVBACKEND_LINUXAIO (value 64, Linux)"
719Use the Linux-specific Linux \s-1AIO\s0 (\fInot\fR \f(CWaio(7)\fR but \f(CWio_submit(2)\fR) event interface available in post\-4.18 kernels (but libev
720only tries to use it in 4.19+).
721.Sp
722This is another Linux train wreck of an event interface.
723.Sp
724If this backend works for you (as of this writing, it was very
725experimental), it is the best event interface available on Linux and might
726be well worth enabling it \- if it isn't available in your kernel this will
727be detected and this backend will be skipped.
728.Sp
729This backend can batch oneshot requests and supports a user-space ring
730buffer to receive events. It also doesn't suffer from most of the design
731problems of epoll (such as not being able to remove event sources from
732the epoll set), and generally sounds too good to be true. Because, this
733being the Linux kernel, of course it suffers from a whole new set of
734limitations, forcing you to fall back to epoll, inheriting all its design
735issues.
736.Sp
737For one, it is not easily embeddable (but probably could be done using
738an event fd at some extra overhead). It also is subject to a system wide
739limit that can be configured in \fI/proc/sys/fs/aio\-max\-nr\fR. If no \s-1AIO\s0
740requests are left, this backend will be skipped during initialisation, and
741will switch to epoll when the loop is active.
742.Sp
743Most problematic in practice, however, is that not all file descriptors
744work with it. For example, in Linux 5.1, \s-1TCP\s0 sockets, pipes, event fds,
745files, \fI/dev/null\fR and many others are supported, but ttys do not work
746properly (a known bug that the kernel developers don't care about, see
747<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
748(yet?) a generic event polling interface.
749.Sp
750Overall, it seems the Linux developers just don't want it to have a
751generic event handling mechanism other than \f(CW\*(C`select\*(C'\fR or \f(CW\*(C`poll\*(C'\fR.
752.Sp
753To work around all these problem, the current version of libev uses its
754epoll backend as a fallback for file descriptor types that do not work. Or
755falls back completely to epoll if the kernel acts up.
700.Sp 756.Sp
701This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as 757This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
702\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. 758\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
703.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 759.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
704.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 760.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
705.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 761.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
706Kqueue deserves special mention, as at the time of this writing, it 762Kqueue deserves special mention, as at the time this backend was
707was broken on all BSDs except NetBSD (usually it doesn't work reliably 763implemented, it was broken on all BSDs except NetBSD (usually it doesn't
708with anything but sockets and pipes, except on Darwin, where of course 764work reliably with anything but sockets and pipes, except on Darwin,
709it's completely useless). Unlike epoll, however, whose brokenness 765where of course it's completely useless). Unlike epoll, however, whose
710is by design, these kqueue bugs can (and eventually will) be fixed 766brokenness is by design, these kqueue bugs can be (and mostly have been)
711without \s-1API\s0 changes to existing programs. For this reason it's not being 767fixed without \s-1API\s0 changes to existing programs. For this reason it's not
712\&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using 768being \*(L"auto-detected\*(R" on all platforms unless you explicitly specify it
713\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) 769in the flags (i.e. using \f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a
714system like NetBSD. 770known-to-be-good (\-enough) system like NetBSD.
715.Sp 771.Sp
716You still can embed kqueue into a normal poll or select backend and use it 772You still can embed kqueue into a normal poll or select backend and use it
717only for sockets (after having made sure that sockets work with kqueue on 773only for sockets (after having made sure that sockets work with kqueue on
718the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 774the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
719.Sp 775.Sp
720It scales in the same way as the epoll backend, but the interface to the 776It scales in the same way as the epoll backend, but the interface to the
721kernel is more efficient (which says nothing about its actual speed, of 777kernel is more efficient (which says nothing about its actual speed, of
722course). While stopping, setting and starting an I/O watcher does never 778course). While stopping, setting and starting an I/O watcher does never
723cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to 779cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
724two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you 780two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you
725might have to leak fd's on fork, but it's more sane than epoll) and it 781might have to leak fds on fork, but it's more sane than epoll) and it
726drops fds silently in similarly hard-to-detect cases. 782drops fds silently in similarly hard-to-detect cases.
727.Sp 783.Sp
728This backend usually performs well under most conditions. 784This backend usually performs well under most conditions.
729.Sp 785.Sp
730While nominally embeddable in other event loops, this doesn't work 786While nominally embeddable in other event loops, this doesn't work
… …
745and is not embeddable, which would limit the usefulness of this backend 801and is not embeddable, which would limit the usefulness of this backend
746immensely. 802immensely.
747.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 803.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
748.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 804.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
749.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 805.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
750This uses the Solaris 10 event port mechanism. As with everything on Solaris, 806This uses the Solaris 10 event port mechanism. As with everything on
751it's really slow, but it still scales very well (O(active_fds)). 807Solaris, it's really slow, but it still scales very well (O(active_fds)).
752.Sp 808.Sp
753While this backend scales well, it requires one system call per active 809While this backend scales well, it requires one system call per active
754file descriptor per loop iteration. For small and medium numbers of file 810file descriptor per loop iteration. For small and medium numbers of file
755descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend 811descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
756might perform better. 812might perform better.
… …
807Example: Use whatever libev has to offer, but make sure that kqueue is 863Example: Use whatever libev has to offer, but make sure that kqueue is
808used if available. 864used if available.
809.Sp 865.Sp
810.Vb 1 866.Vb 1
811\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); 867\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
868.Ve
869.Sp
870Example: Similarly, on linux, you mgiht want to take advantage of the
871linux aio backend if possible, but fall back to something else if that
872isn't available.
873.Sp
874.Vb 1
875\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
812.Ve 876.Ve
813.RE 877.RE
814.IP "ev_loop_destroy (loop)" 4 878.IP "ev_loop_destroy (loop)" 4
815.IX Item "ev_loop_destroy (loop)" 879.IX Item "ev_loop_destroy (loop)"
816Destroys an event loop object (frees all memory and kernel state 880Destroys an event loop object (frees all memory and kernel state
… …
1023\& \- Queue all expired timers. 1087\& \- Queue all expired timers.
1024\& \- Queue all expired periodics. 1088\& \- Queue all expired periodics.
1025\& \- Queue all idle watchers with priority higher than that of pending events. 1089\& \- Queue all idle watchers with priority higher than that of pending events.
1026\& \- Queue all check watchers. 1090\& \- Queue all check watchers.
1027\& \- Call all queued watchers in reverse order (i.e. check watchers first). 1091\& \- Call all queued watchers in reverse order (i.e. check watchers first).
1028\& Signals and child watchers are implemented as I/O watchers, and will 1092\& Signals, async and child watchers are implemented as I/O watchers, and
1029\& be handled here by queueing them when their watcher gets executed. 1093\& will be handled here by queueing them when their watcher gets executed.
1030\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT 1094\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
1031\& were used, or there are no active watchers, goto FINISH, otherwise 1095\& were used, or there are no active watchers, goto FINISH, otherwise
1032\& continue with step LOOP. 1096\& continue with step LOOP.
1033\& FINISH: 1097\& FINISH:
1034\& \- Reset the ev_break status iff it was EVBREAK_ONE. 1098\& \- Reset the ev_break status iff it was EVBREAK_ONE.
… …
1285with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher 1349with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher
1286*)\*(C'\fR), and you can stop watching for events at any time by calling the 1350*)\*(C'\fR), and you can stop watching for events at any time by calling the
1287corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR. 1351corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR.
1288.PP 1352.PP
1289As long as your watcher is active (has been started but not stopped) you 1353As long as your watcher is active (has been started but not stopped) you
1290must not touch the values stored in it. Most specifically you must never 1354must not touch the values stored in it except when explicitly documented
1291reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro. 1355otherwise. Most specifically you must never reinitialise it or call its
1356\&\f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
1292.PP 1357.PP
1293Each and every callback receives the event loop pointer as first, the 1358Each and every callback receives the event loop pointer as first, the
1294registered watcher structure as second, and a bitset of received events as 1359registered watcher structure as second, and a bitset of received events as
1295third argument. 1360third argument.
1296.PP 1361.PP
… …
1467therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. 1532therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
1468.IP "bool ev_is_active (ev_TYPE *watcher)" 4 1533.IP "bool ev_is_active (ev_TYPE *watcher)" 4
1469.IX Item "bool ev_is_active (ev_TYPE *watcher)" 1534.IX Item "bool ev_is_active (ev_TYPE *watcher)"
1470Returns a true value iff the watcher is active (i.e. it has been started 1535Returns a true value iff the watcher is active (i.e. it has been started
1471and not yet been stopped). As long as a watcher is active you must not modify 1536and not yet been stopped). As long as a watcher is active you must not modify
1472it. 1537it unless documented otherwise.
1538.Sp
1539Obviously, it is safe to call this on an active watcher, or actually any
1540watcher that is initialised.
1473.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 1541.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
1474.IX Item "bool ev_is_pending (ev_TYPE *watcher)" 1542.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
1475Returns a true value iff the watcher is pending, (i.e. it has outstanding 1543Returns a true value iff the watcher is pending, (i.e. it has outstanding
1476events but its callback has not yet been invoked). As long as a watcher 1544events but its callback has not yet been invoked). As long as a watcher
1477is pending (but not active) you must not call an init function on it (but 1545is pending (but not active) you must not call an init function on it (but
1478\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must 1546\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
1479make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR 1547make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
1480it). 1548it).
1549.Sp
1550It is safe to call this on any watcher in any state as long as it is
1551initialised.
1481.IP "callback ev_cb (ev_TYPE *watcher)" 4 1552.IP "callback ev_cb (ev_TYPE *watcher)" 4
1482.IX Item "callback ev_cb (ev_TYPE *watcher)" 1553.IX Item "callback ev_cb (ev_TYPE *watcher)"
1483Returns the callback currently set on the watcher. 1554Returns the callback currently set on the watcher.
1484.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4 1555.IP "ev_set_cb (ev_TYPE *watcher, callback)" 4
1485.IX Item "ev_set_cb (ev_TYPE *watcher, callback)" 1556.IX Item "ev_set_cb (ev_TYPE *watcher, callback)"
… …
1498from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). 1569from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
1499.Sp 1570.Sp
1500If you need to suppress invocation when higher priority events are pending 1571If you need to suppress invocation when higher priority events are pending
1501you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. 1572you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
1502.Sp 1573.Sp
1503You \fImust not\fR change the priority of a watcher as long as it is active or 1574You \fImust not\fR change the priority of a watcher as long as it is active
1504pending. 1575or pending. Reading the priority with \f(CW\*(C`ev_priority\*(C'\fR is fine in any state.
1505.Sp 1576.Sp
1506Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is 1577Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
1507fine, as long as you do not mind that the priority value you query might 1578fine, as long as you do not mind that the priority value you query might
1508or might not have been clamped to the valid range. 1579or might not have been clamped to the valid range.
1509.Sp 1580.Sp
… …
1528callback to be invoked, which can be accomplished with this function. 1599callback to be invoked, which can be accomplished with this function.
1529.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4 1600.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4
1530.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 1601.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)"
1531Feeds the given event set into the event loop, as if the specified event 1602Feeds the given event set into the event loop, as if the specified event
1532had happened for the specified watcher (which must be a pointer to an 1603had happened for the specified watcher (which must be a pointer to an
1533initialised but not necessarily started event watcher). Obviously you must 1604initialised but not necessarily started event watcher, though it can be
1534not free the watcher as long as it has pending events. 1605active). Obviously you must not free the watcher as long as it has pending
1606events.
1535.Sp 1607.Sp
1536Stopping the watcher, letting libev invoke it, or calling 1608Stopping the watcher, letting libev invoke it, or calling
1537\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was 1609\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was
1538not started in the first place. 1610not started in the first place.
1539.Sp 1611.Sp
… …
1560\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again. 1632\&\f(CW\*(C`ev_TYPE_init\*(C'\fR again.
1561.IP "started/running/active" 4 1633.IP "started/running/active" 4
1562.IX Item "started/running/active" 1634.IX Item "started/running/active"
1563Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes 1635Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes
1564property of the event loop, and is actively waiting for events. While in 1636property of the event loop, and is actively waiting for events. While in
1565this state it cannot be accessed (except in a few documented ways), moved, 1637this state it cannot be accessed (except in a few documented ways, such as
1566freed or anything else \- the only legal thing is to keep a pointer to it, 1638stoping it), moved, freed or anything else \- the only legal thing is to
1567and call libev functions on it that are documented to work on active watchers. 1639keep a pointer to it, and call libev functions on it that are documented
1640to work on active watchers.
1641.Sp
1642As a rule of thumb, before accessing a member or calling any function on
1643a watcher, it should be stopped (or freshly initialised). If that is not
1644convenient, you can check the documentation for that function or member to
1645see if it is safe to use on an active watcher.
1568.IP "pending" 4 1646.IP "pending" 4
1569.IX Item "pending" 1647.IX Item "pending"
1570If a watcher is active and libev determines that an event it is interested 1648If a watcher is active and libev determines that an event it is interested
1571in has occurred (such as a timer expiring), it will become pending. It will 1649in has occurred (such as a timer expiring), it will become pending. It
1572stay in this pending state until either it is stopped or its callback is 1650will stay in this pending state until either it is explicitly stopped or
1573about to be invoked, so it is not normally pending inside the watcher 1651its callback is about to be invoked, so it is not normally pending inside
1574callback. 1652the watcher callback.
1575.Sp 1653.Sp
1576The watcher might or might not be active while it is pending (for example, 1654Generally, the watcher might or might not be active while it is pending
1577an expired non-repeating timer can be pending but no longer active). If it 1655(for example, an expired non-repeating timer can be pending but no longer
1578is stopped, it can be freely accessed (e.g. by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR), 1656active). If it is pending but not active, it can be freely accessed (e.g.
1579but it is still property of the event loop at this time, so cannot be 1657by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR), but it is still property of the event loop at
1580moved, freed or reused. And if it is active the rules described in the 1658this time, so cannot be moved, freed or reused. And if it is active the
1581previous item still apply. 1659rules described in the previous item still apply.
1660.Sp
1661Explicitly stopping a watcher will also clear the pending state
1662unconditionally, so it is safe to stop a watcher and then free it.
1582.Sp 1663.Sp
1583It is also possible to feed an event on a watcher that is not active (e.g. 1664It is also possible to feed an event on a watcher that is not active (e.g.
1584via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being 1665via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being
1585active. 1666active.
1586.IP "stopped" 4 1667.IP "stopped" 4
… …
1599.IX Subsection "WATCHER PRIORITY MODELS" 1680.IX Subsection "WATCHER PRIORITY MODELS"
1600Many event loops support \fIwatcher priorities\fR, which are usually small 1681Many event loops support \fIwatcher priorities\fR, which are usually small
1601integers that influence the ordering of event callback invocation 1682integers that influence the ordering of event callback invocation
1602between watchers in some way, all else being equal. 1683between watchers in some way, all else being equal.
1603.PP 1684.PP
1604In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its 1685In libev, watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
1605description for the more technical details such as the actual priority 1686description for the more technical details such as the actual priority
1606range. 1687range.
1607.PP 1688.PP
1608There are two common ways how these these priorities are being interpreted 1689There are two common ways how these these priorities are being interpreted
1609by event loops: 1690by event loops:
… …
1703.IX Header "WATCHER TYPES" 1784.IX Header "WATCHER TYPES"
1704This section describes each watcher in detail, but will not repeat 1785This section describes each watcher in detail, but will not repeat
1705information given in the last section. Any initialisation/set macros, 1786information given in the last section. Any initialisation/set macros,
1706functions and members specific to the watcher type are explained. 1787functions and members specific to the watcher type are explained.
1707.PP 1788.PP
1708Members are additionally marked with either \fI[read\-only]\fR, meaning that, 1789Most members are additionally marked with either \fI[read\-only]\fR, meaning
1709while the watcher is active, you can look at the member and expect some 1790that, while the watcher is active, you can look at the member and expect
1710sensible content, but you must not modify it (you can modify it while the 1791some sensible content, but you must not modify it (you can modify it while
1711watcher is stopped to your hearts content), or \fI[read\-write]\fR, which 1792the watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1712means you can expect it to have some sensible content while the watcher 1793means you can expect it to have some sensible content while the watcher is
1713is active, but you can also modify it. Modifying it may not do something 1794active, but you can also modify it (within the same thread as the event
1795loop, i.e. without creating data races). Modifying it may not do something
1714sensible or take immediate effect (or do anything at all), but libev will 1796sensible or take immediate effect (or do anything at all), but libev will
1715not crash or malfunction in any way. 1797not crash or malfunction in any way.
1798.PP
1799In any case, the documentation for each member will explain what the
1800effects are, and if there are any additional access restrictions.
1716.ie n .SS """ev_io"" \- is this file descriptor readable or writable?" 1801.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
1717.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" 1802.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
1718.IX Subsection "ev_io - is this file descriptor readable or writable?" 1803.IX Subsection "ev_io - is this file descriptor readable or writable?"
1719I/O watchers check whether a file descriptor is readable or writable 1804I/O watchers check whether a file descriptor is readable or writable
1720in each iteration of the event loop, or, more precisely, when reading 1805in each iteration of the event loop, or, more precisely, when reading
… …
1748But really, best use non-blocking mode. 1833But really, best use non-blocking mode.
1749.PP 1834.PP
1750\fIThe special problem of disappearing file descriptors\fR 1835\fIThe special problem of disappearing file descriptors\fR
1751.IX Subsection "The special problem of disappearing file descriptors" 1836.IX Subsection "The special problem of disappearing file descriptors"
1752.PP 1837.PP
1753Some backends (e.g. kqueue, epoll) need to be told about closing a file 1838Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1754descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means, 1839a file descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other
1755such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file 1840means, such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some
1756descriptor, but when it goes away, the operating system will silently drop 1841file descriptor, but when it goes away, the operating system will silently
1757this interest. If another file descriptor with the same number then is 1842drop this interest. If another file descriptor with the same number then
1758registered with libev, there is no efficient way to see that this is, in 1843is registered with libev, there is no efficient way to see that this is,
1759fact, a different file descriptor. 1844in fact, a different file descriptor.
1760.PP 1845.PP
1761To avoid having to explicitly tell libev about such cases, libev follows 1846To avoid having to explicitly tell libev about such cases, libev follows
1762the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev 1847the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1763will assume that this is potentially a new file descriptor, otherwise 1848will assume that this is potentially a new file descriptor, otherwise
1764it is assumed that the file descriptor stays the same. That means that 1849it is assumed that the file descriptor stays the same. That means that
… …
1816reuse the same code path. 1901reuse the same code path.
1817.PP 1902.PP
1818\fIThe special problem of fork\fR 1903\fIThe special problem of fork\fR
1819.IX Subsection "The special problem of fork" 1904.IX Subsection "The special problem of fork"
1820.PP 1905.PP
1821Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit 1906Some backends (epoll, kqueue, linuxaio, iouring) do not support \f(CW\*(C`fork ()\*(C'\fR
1822useless behaviour. Libev fully supports fork, but needs to be told about 1907at all or exhibit useless behaviour. Libev fully supports fork, but needs
1823it in the child if you want to continue to use it in the child. 1908to be told about it in the child if you want to continue to use it in the
1909child.
1824.PP 1910.PP
1825To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork 1911To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
1826()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to 1912()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to
1827\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. 1913\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1828.PP 1914.PP
… …
1885.PD 0 1971.PD 0
1886.IP "ev_io_set (ev_io *, int fd, int events)" 4 1972.IP "ev_io_set (ev_io *, int fd, int events)" 4
1887.IX Item "ev_io_set (ev_io *, int fd, int events)" 1973.IX Item "ev_io_set (ev_io *, int fd, int events)"
1888.PD 1974.PD
1889Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to 1975Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
1890receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or 1976receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR, both
1891\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. 1977\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR or \f(CW0\fR, to express the desire to receive the given
1978events.
1979.Sp
1980Note that setting the \f(CW\*(C`events\*(C'\fR to \f(CW0\fR and starting the watcher is
1981supported, but not specially optimized \- if your program sometimes happens
1982to generate this combination this is fine, but if it is easy to avoid
1983starting an io watcher watching for no events you should do so.
1984.IP "ev_io_modify (ev_io *, int events)" 4
1985.IX Item "ev_io_modify (ev_io *, int events)"
1986Similar to \f(CW\*(C`ev_io_set\*(C'\fR, but only changes the requested events. Using this
1987might be faster with some backends, as libev can assume that the \f(CW\*(C`fd\*(C'\fR
1988still refers to the same underlying file description, something it cannot
1989do when using \f(CW\*(C`ev_io_set\*(C'\fR.
1892.IP "int fd [read\-only]" 4 1990.IP "int fd [no\-modify]" 4
1893.IX Item "int fd [read-only]" 1991.IX Item "int fd [no-modify]"
1894The file descriptor being watched. 1992The file descriptor being watched. While it can be read at any time, you
1993must not modify this member even when the watcher is stopped \- always use
1994\&\f(CW\*(C`ev_io_set\*(C'\fR for that.
1895.IP "int events [read\-only]" 4 1995.IP "int events [no\-modify]" 4
1896.IX Item "int events [read-only]" 1996.IX Item "int events [no-modify]"
1897The events being watched. 1997The set of events the fd is being watched for, among other flags. Remember
1998that this is a bit set \- to test for \f(CW\*(C`EV_READ\*(C'\fR, use \f(CW\*(C`w\->events &
1999EV_READ\*(C'\fR, and similarly for \f(CW\*(C`EV_WRITE\*(C'\fR.
2000.Sp
2001As with \f(CW\*(C`fd\*(C'\fR, you must not modify this member even when the watcher is
2002stopped, always use \f(CW\*(C`ev_io_set\*(C'\fR or \f(CW\*(C`ev_io_modify\*(C'\fR for that.
1898.PP 2003.PP
1899\fIExamples\fR 2004\fIExamples\fR
1900.IX Subsection "Examples" 2005.IX Subsection "Examples"
1901.PP 2006.PP
1902Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 2007Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
… …
3913.PP 4018.PP
3914First, you need to associate some data with the event loop: 4019First, you need to associate some data with the event loop:
3915.PP 4020.PP
3916.Vb 6 4021.Vb 6
3917\& typedef struct { 4022\& typedef struct {
3918\& mutex_t lock; /* global loop lock */ 4023\& pthread_mutex_t lock; /* global loop lock */
4024\& pthread_t tid;
4025\& pthread_cond_t invoke_cv;
3919\& ev_async async_w; 4026\& ev_async async_w;
3920\& thread_t tid;
3921\& cond_t invoke_cv;
3922\& } userdata; 4027\& } userdata;
3923\& 4028\&
3924\& void prepare_loop (EV_P) 4029\& void prepare_loop (EV_P)
3925\& { 4030\& {
3926\& // for simplicity, we use a static userdata struct. 4031\& // for simplicity, we use a static userdata struct.
3927\& static userdata u; 4032\& static userdata u;
3928\& 4033\&
3929\& ev_async_init (&u\->async_w, async_cb); 4034\& ev_async_init (&u.async_w, async_cb);
3930\& ev_async_start (EV_A_ &u\->async_w); 4035\& ev_async_start (EV_A_ &u.async_w);
3931\& 4036\&
3932\& pthread_mutex_init (&u\->lock, 0); 4037\& pthread_mutex_init (&u.lock, 0);
3933\& pthread_cond_init (&u\->invoke_cv, 0); 4038\& pthread_cond_init (&u.invoke_cv, 0);
3934\& 4039\&
3935\& // now associate this with the loop 4040\& // now associate this with the loop
3936\& ev_set_userdata (EV_A_ u); 4041\& ev_set_userdata (EV_A_ &u);
3937\& ev_set_invoke_pending_cb (EV_A_ l_invoke); 4042\& ev_set_invoke_pending_cb (EV_A_ l_invoke);
3938\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire); 4043\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3939\& 4044\&
3940\& // then create the thread running ev_run 4045\& // then create the thread running ev_run
3941\& pthread_create (&u\->tid, 0, l_run, EV_A); 4046\& pthread_create (&u.tid, 0, l_run, EV_A);
3942\& } 4047\& }
3943.Ve 4048.Ve
3944.PP 4049.PP
3945The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used 4050The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
3946solely to wake up the event loop so it takes notice of any new watchers 4051solely to wake up the event loop so it takes notice of any new watchers
… …
4330gets automatically stopped and restarted when reconfiguring it with this 4435gets automatically stopped and restarted when reconfiguring it with this
4331method. 4436method.
4332.Sp 4437.Sp
4333For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid 4438For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
4334clashing with the \f(CW\*(C`set (loop)\*(C'\fR method. 4439clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
4440.Sp
4441For \f(CW\*(C`ev::io\*(C'\fR watchers there is an additional \f(CW\*(C`set\*(C'\fR method that acepts a
4442new event mask only, and internally calls \f(CW\*(C`ev_io_modify\*(C'\fR.
4335.IP "w\->start ()" 4 4443.IP "w\->start ()" 4
4336.IX Item "w->start ()" 4444.IX Item "w->start ()"
4337Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the 4445Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
4338constructor already stores the event loop. 4446constructor already stores the event loop.
4339.IP "w\->start ([arguments])" 4 4447.IP "w\->start ([arguments])" 4
… …
4567\& ev_win32.c required on win32 platforms only 4675\& ev_win32.c required on win32 platforms only
4568\& 4676\&
4569\& ev_select.c only when select backend is enabled 4677\& ev_select.c only when select backend is enabled
4570\& ev_poll.c only when poll backend is enabled 4678\& ev_poll.c only when poll backend is enabled
4571\& ev_epoll.c only when the epoll backend is enabled 4679\& ev_epoll.c only when the epoll backend is enabled
4680\& ev_linuxaio.c only when the linux aio backend is enabled
4681\& ev_iouring.c only when the linux io_uring backend is enabled
4572\& ev_kqueue.c only when the kqueue backend is enabled 4682\& ev_kqueue.c only when the kqueue backend is enabled
4573\& ev_port.c only when the solaris port backend is enabled 4683\& ev_port.c only when the solaris port backend is enabled
4574.Ve 4684.Ve
4575.PP 4685.PP
4576\&\fIev.c\fR includes the backend files directly when enabled, so you only need 4686\&\fIev.c\fR includes the backend files directly when enabled, so you only need
… …
4689higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). 4799higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
4690.IP "\s-1EV_USE_NANOSLEEP\s0" 4 4800.IP "\s-1EV_USE_NANOSLEEP\s0" 4
4691.IX Item "EV_USE_NANOSLEEP" 4801.IX Item "EV_USE_NANOSLEEP"
4692If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available 4802If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
4693and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. 4803and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
4804.IP "\s-1EV_USE_EVENTFD\s0" 4
4805.IX Item "EV_USE_EVENTFD"
4806If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4807available and will probe for kernel support at runtime. This will improve
4808\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
4809If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
48102.7 or newer, otherwise disabled.
4811.IP "\s-1EV_USE_SIGNALFD\s0" 4
4812.IX Item "EV_USE_SIGNALFD"
4813If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`signalfd ()\*(C'\fR is
4814available and will probe for kernel support at runtime. This enables
4815the use of \s-1EVFLAG_SIGNALFD\s0 for faster and simpler signal handling. If
4816undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
48172.7 or newer, otherwise disabled.
4818.IP "\s-1EV_USE_TIMERFD\s0" 4
4819.IX Item "EV_USE_TIMERFD"
4820If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`timerfd ()\*(C'\fR is
4821available and will probe for kernel support at runtime. This allows
4822libev to detect time jumps accurately. If undefined, it will be enabled
4823if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
4824\&\f(CW\*(C`TFD_TIMER_CANCEL_ON_SET\*(C'\fR, otherwise disabled.
4694.IP "\s-1EV_USE_EVENTFD\s0" 4 4825.IP "\s-1EV_USE_EVENTFD\s0" 4
4695.IX Item "EV_USE_EVENTFD" 4826.IX Item "EV_USE_EVENTFD"
4696If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is 4827If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4697available and will probe for kernel support at runtime. This will improve 4828available and will probe for kernel support at runtime. This will improve
4698\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. 4829\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
… …
4757If defined to be \f(CW1\fR, libev will compile in support for the Linux 4888If defined to be \f(CW1\fR, libev will compile in support for the Linux
4758\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, 4889\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
4759otherwise another method will be used as fallback. This is the preferred 4890otherwise another method will be used as fallback. This is the preferred
4760backend for GNU/Linux systems. If undefined, it will be enabled if the 4891backend for GNU/Linux systems. If undefined, it will be enabled if the
4761headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. 4892headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4893.IP "\s-1EV_USE_LINUXAIO\s0" 4
4894.IX Item "EV_USE_LINUXAIO"
4895If defined to be \f(CW1\fR, libev will compile in support for the Linux aio
4896backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). If undefined, it will be
4897enabled on linux, otherwise disabled.
4898.IP "\s-1EV_USE_IOURING\s0" 4
4899.IX Item "EV_USE_IOURING"
4900If defined to be \f(CW1\fR, libev will compile in support for the Linux
4901io_uring backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). Due to it's
4902current limitations it has to be requested explicitly. If undefined, it
4903will be enabled on linux, otherwise disabled.
4762.IP "\s-1EV_USE_KQUEUE\s0" 4 4904.IP "\s-1EV_USE_KQUEUE\s0" 4
4763.IX Item "EV_USE_KQUEUE" 4905.IX Item "EV_USE_KQUEUE"
4764If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style 4906If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
4765\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, 4907\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
4766otherwise another method will be used as fallback. This is the preferred 4908otherwise another method will be used as fallback. This is the preferred
… …
5022in. If set to \f(CW1\fR, then verification code will be compiled in, but not 5164in. If set to \f(CW1\fR, then verification code will be compiled in, but not
5023called. If set to \f(CW2\fR, then the internal verification code will be 5165called. If set to \f(CW2\fR, then the internal verification code will be
5024called once per loop, which can slow down libev. If set to \f(CW3\fR, then the 5166called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
5025verification code will be called very frequently, which will slow down 5167verification code will be called very frequently, which will slow down
5026libev considerably. 5168libev considerably.
5169.Sp
5170Verification errors are reported via C's \f(CW\*(C`assert\*(C'\fR mechanism, so if you
5171disable that (e.g. by defining \f(CW\*(C`NDEBUG\*(C'\fR) then no errors will be reported.
5027.Sp 5172.Sp
5028The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it 5173The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
5029will be \f(CW0\fR. 5174will be \f(CW0\fR.
5030.IP "\s-1EV_COMMON\s0" 4 5175.IP "\s-1EV_COMMON\s0" 4
5031.IX Item "EV_COMMON" 5176.IX Item "EV_COMMON"

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