[ViewVC] Diff of: cvs/libev/ev.3

Comparing libev/ev.3 (file contents):
Revision 1.69 by root, Sat Jul 5 02:25:40 2008 UTC vs.
Revision 1.79 by root, Fri Jul 17 14:43:38 2009 UTC

-.\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05)
+.\" Automatically generated by Pod::Man 2.22 (Pod::Simple 3.07)
 .\"
 .\" Standard preamble:
 .\" ========================================================================
-.de Sh \" Subsection heading
-.br
-.if t .Sp
-.ne 5
-.PP
-\fB\\$1\fR
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-.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
+.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
 .\" entries marked with X<> in POD.  Of course, you'll have to process the
 .\" output yourself in some meaningful fashion.
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 .    de IX
 .    tm Index:\\$1\t\\n%\t"\\$2"
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 .IX Title "LIBEV 3"
-.TH LIBEV 3 "2008-06-19" "libev-3.43" "libev - high performance full featured event loop"
+.TH LIBEV 3 "2009-07-15" "libev-3.7" "libev - high performance full featured event loop"
 .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
 .\" way too many mistakes in technical documents.
 .if n .ad l
 .nh
 .SH "NAME"
 .SH "SYNOPSIS"
 .IX Header "SYNOPSIS"
 .Vb 1
 \&   #include <ev.h>
 .Ve
-.Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0"
+.SS "\s-1EXAMPLE\s0 \s-1PROGRAM\s0"
 .IX Subsection "EXAMPLE PROGRAM"
 .Vb 2
 \&   // a single header file is required
 \&   #include <ev.h>
 \&
+\&   #include <stdio.h> // for puts
+\&
 \&   // every watcher type has its own typedef\*(Aqd struct
-\&   // with the name ev_<type>
+\&   // with the name ev_TYPE
 \&   ev_io stdin_watcher;
 \&   ev_timer timeout_watcher;
 \&
 \&   // all watcher callbacks have a similar signature
 \&   // this callback is called when data is readable on stdin
 \&   static void
-\&   stdin_cb (EV_P_ struct ev_io *w, int revents)
+\&   stdin_cb (EV_P_ ev_io *w, int revents)
 \&   {
 \&     puts ("stdin ready");
 \&     // for one\-shot events, one must manually stop the watcher
 \&     // with its corresponding stop function.
 \&     ev_io_stop (EV_A_ w);
 \&     ev_unloop (EV_A_ EVUNLOOP_ALL);
 \&   }
 \&
 \&   // another callback, this time for a time\-out
 \&   static void
-\&   timeout_cb (EV_P_ struct ev_timer *w, int revents)
+\&   timeout_cb (EV_P_ ev_timer *w, int revents)
 \&   {
 \&     puts ("timeout");
 \&     // this causes the innermost ev_loop to stop iterating
 \&     ev_unloop (EV_A_ EVUNLOOP_ONE);
 \&   }
 \&
 \&     // unloop was called, so exit
 \&     return 0;
 \&   }
 .Ve
-.SH "DESCRIPTION"
+.SH "ABOUT THIS DOCUMENT"
-.IX Header "DESCRIPTION"
+.IX Header "ABOUT THIS DOCUMENT"
+This document documents the libev software package.
+.PP
 The newest version of this document is also available as an html-formatted
 web page you might find easier to navigate when reading it for the first
 time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
 .PP
+While this document tries to be as complete as possible in documenting
+libev, its usage and the rationale behind its design, it is not a tutorial
+on event-based programming, nor will it introduce event-based programming
+with libev.
+.PP
+Familarity with event based programming techniques in general is assumed
+throughout this document.
+.SH "ABOUT LIBEV"
+.IX Header "ABOUT LIBEV"
 Libev is an event loop: you register interest in certain events (such as a
 file descriptor being readable or a timeout occurring), and it will manage
 these event sources and provide your program with events.
 .PP
 To do this, it must take more or less complete control over your process
 .PP
 You register interest in certain events by registering so-called \fIevent
 watchers\fR, which are relatively small C structures you initialise with the
 details of the event, and then hand it over to libev by \fIstarting\fR the
 watcher.
-.Sh "\s-1FEATURES\s0"
+.SS "\s-1FEATURES\s0"
 .IX Subsection "FEATURES"
 Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
 BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
 for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
 (for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
 \&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as
 file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
 (\f(CW\*(C`ev_fork\*(C'\fR).
 .PP
 It also is quite fast (see this
-benchmark comparing it to libevent
+<benchmark> comparing it to libevent
 for example).
-.Sh "\s-1CONVENTIONS\s0"
+.SS "\s-1CONVENTIONS\s0"
 .IX Subsection "CONVENTIONS"
 Libev is very configurable. In this manual the default (and most common)
 configuration will be described, which supports multiple event loops. For
 more info about various configuration options please have a look at
 \&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support
 for multiple event loops, then all functions taking an initial argument of
-name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have
+name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`ev_loop *\*(C'\fR) will not have
 this argument.
-.Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0"
+.SS "\s-1TIME\s0 \s-1REPRESENTATION\s0"
 .IX Subsection "TIME REPRESENTATION"
-Libev represents time as a single floating point number, representing the
+Libev represents time as a single floating point number, representing
-(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
+the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere
-the beginning of 1970, details are complicated, don't ask). This type is
+near the beginning of 1970, details are complicated, don't ask). This
-called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
+type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually
-to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
+aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do any calculations
-it, you should treat it as some floating point value. Unlike the name
+on it, you should treat it as some floating point value. Unlike the name
 component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences
 throughout libev.
 .SH "ERROR HANDLING"
 .IX Header "ERROR HANDLING"
 Libev knows three classes of errors: operating system errors, usage errors
 might be supported on the current system, you would need to look at
 \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
 recommended ones.
 .Sp
 See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
-.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
+.IP "ev_set_allocator (void *(*cb)(void *ptr, long size)) [\s-1NOT\s0 \s-1REENTRANT\s0]" 4
-.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
+.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]"
 Sets the allocation function to use (the prototype is similar \- the
 semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is
 used to allocate and free memory (no surprises here). If it returns zero
 when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort
 or take some potentially destructive action.
 \&   }
 \&
 \&   ...
 \&   ev_set_allocator (persistent_realloc);
 .Ve
-.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
+.IP "ev_set_syserr_cb (void (*cb)(const char *msg)); [\s-1NOT\s0 \s-1REENTRANT\s0]" 4
-.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
+.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]"
 Set the callback function to call on a retryable system call error (such
 as failed select, poll, epoll_wait). The message is a printable string
 indicating the system call or subsystem causing the problem. If this
 callback is set, then libev will expect it to remedy the situation, no
 matter what, when it returns. That is, libev will generally retry the
 \&   ...
 \&   ev_set_syserr_cb (fatal_error);
 .Ve
 .SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
 .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
-An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
+An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR
-types of such loops, the \fIdefault\fR loop, which supports signals and child
+is \fInot\fR optional in this case, as there is also an \f(CW\*(C`ev_loop\*(C'\fR
-events, and dynamically created loops which do not.
+\&\fIfunction\fR).
+.PP
+The library knows two types of such loops, the \fIdefault\fR loop, which
+supports signals and child events, and dynamically created loops which do
+not.
 .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
 .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
 This will initialise the default event loop if it hasn't been initialised
 yet and return it. If the default loop could not be initialised, returns
 false. If it already was initialised it simply returns it (and ignores the
 If you don't know what event loop to use, use the one returned from this
 function.
 .Sp
 Note that this function is \fInot\fR thread-safe, so if you want to use it
 from multiple threads, you have to lock (note also that this is unlikely,
-as loops cannot bes hared easily between threads anyway).
+as loops cannot be shared easily between threads anyway).
 .Sp
 The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and
 \&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler
 for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either
 create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you
 parallelism (most of the file descriptors should be busy). If you are
 writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many
 connections as possible during one iteration. You might also want to have
 a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of
 readiness notifications you get per iteration.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the
+\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the
+\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform).
 .ie n .IP """EVBACKEND_POLL""    (value 2, poll backend, available everywhere except on windows)" 4
 .el .IP "\f(CWEVBACKEND_POLL\fR    (value 2, poll backend, available everywhere except on windows)" 4
 .IX Item "EVBACKEND_POLL    (value 2, poll backend, available everywhere except on windows)"
 And this is your standard \fIpoll\fR\|(2) backend. It's more complicated
 than select, but handles sparse fds better and has no artificial
 limit on the number of fds you can use (except it will slow down
 considerably with a lot of inactive fds). It scales similarly to select,
 i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
 performance tips.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
+\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
 .ie n .IP """EVBACKEND_EPOLL""   (value 4, Linux)" 4
 .el .IP "\f(CWEVBACKEND_EPOLL\fR   (value 4, Linux)" 4
 .IX Item "EVBACKEND_EPOLL   (value 4, Linux)"
 For few fds, this backend is a bit little slower than poll and select,
 but it scales phenomenally better. While poll and select usually scale
 like O(total_fds) where n is the total number of fds (or the highest fd),
-epoll scales either O(1) or O(active_fds). The epoll design has a number
+epoll scales either O(1) or O(active_fds).
-of shortcomings, such as silently dropping events in some hard-to-detect
+.Sp
-cases and requiring a system call per fd change, no fork support and bad
+The epoll mechanism deserves honorable mention as the most misdesigned
-support for dup.
+of the more advanced event mechanisms: mere annoyances include silently
+dropping file descriptors, requiring a system call per change per file
+descriptor (and unnecessary guessing of parameters), problems with dup and
+so on. The biggest issue is fork races, however \- if a program forks then
+\&\fIboth\fR parent and child process have to recreate the epoll set, which can
+take considerable time (one syscall per file descriptor) and is of course
+hard to detect.
+.Sp
+Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, but
+of course \fIdoesn't\fR, and epoll just loves to report events for totally
+\&\fIdifferent\fR file descriptors (even already closed ones, so one cannot
+even remove them from the set) than registered in the set (especially
+on \s-1SMP\s0 systems). Libev tries to counter these spurious notifications by
+employing an additional generation counter and comparing that against the
+events to filter out spurious ones, recreating the set when required.
 .Sp
 While stopping, setting and starting an I/O watcher in the same iteration
-will result in some caching, there is still a system call per such incident
+will result in some caching, there is still a system call per such
-(because the fd could point to a different file description now), so its
+incident (because the same \fIfile descriptor\fR could point to a different
-best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work
+\&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed
-very well if you register events for both fds.
+file descriptors might not work very well if you register events for both
-.Sp
+file descriptors.
-Please note that epoll sometimes generates spurious notifications, so you
-need to use non-blocking I/O or other means to avoid blocking when no data
-(or space) is available.
 .Sp
 Best performance from this backend is achieved by not unregistering all
-watchers for a file descriptor until it has been closed, if possible, i.e.
+watchers for a file descriptor until it has been closed, if possible,
-keep at least one watcher active per fd at all times.
+i.e. keep at least one watcher active per fd at all times. Stopping and
+starting a watcher (without re-setting it) also usually doesn't cause
+extra overhead. A fork can both result in spurious notifications as well
+as in libev having to destroy and recreate the epoll object, which can
+take considerable time and thus should be avoided.
+.Sp
+All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or
+faster than epoll for maybe up to a hundred file descriptors, depending on
+the usage. So sad.
 .Sp
 While nominally embeddable in other event loops, this feature is broken in
 all kernel versions tested so far.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
 .ie n .IP """EVBACKEND_KQUEUE""  (value 8, most \s-1BSD\s0 clones)" 4
 .el .IP "\f(CWEVBACKEND_KQUEUE\fR  (value 8, most \s-1BSD\s0 clones)" 4
 .IX Item "EVBACKEND_KQUEUE  (value 8, most BSD clones)"
 Kqueue deserves special mention, as at the time of this writing, it
 was broken on all BSDs except NetBSD (usually it doesn't work reliably
 with anything but sockets and pipes, except on Darwin, where of course
-it's completely useless). For this reason it's not being \*(L"auto-detected\*(R"
+it's completely useless). Unlike epoll, however, whose brokenness
+is by design, these kqueue bugs can (and eventually will) be fixed
+without \s-1API\s0 changes to existing programs. For this reason it's not being
-unless you explicitly specify it explicitly in the flags (i.e. using
+\&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using
 \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
 system like NetBSD.
 .Sp
 You still can embed kqueue into a normal poll or select backend and use it
 only for sockets (after having made sure that sockets work with kqueue on
 .Sp
 It scales in the same way as the epoll backend, but the interface to the
 kernel is more efficient (which says nothing about its actual speed, of
 course). While stopping, setting and starting an I/O watcher does never
 cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
-two event changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it
+two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (but
-drops fds silently in similarly hard-to-detect cases.
+sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
+cases
 .Sp
 This backend usually performs well under most conditions.
 .Sp
 While nominally embeddable in other event loops, this doesn't work
 everywhere, so you might need to test for this. And since it is broken
 almost everywhere, you should only use it when you have a lot of sockets
 (for which it usually works), by embedding it into another event loop
-(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR) and using it only for
+(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course
-sockets.
+also broken on \s-1OS\s0 X)) and, did I mention it, using it only for sockets.
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with
+\&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with
+\&\f(CW\*(C`NOTE_EOF\*(C'\fR.
 .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
 .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
 .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
 This is not implemented yet (and might never be, unless you send me an
 implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets
 While this backend scales well, it requires one system call per active
 file descriptor per loop iteration. For small and medium numbers of file
 descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
 might perform better.
 .Sp
-On the positive side, ignoring the spurious readiness notifications, this
+On the positive side, with the exception of the spurious readiness
-backend actually performed to specification in all tests and is fully
+notifications, this backend actually performed fully to specification
-embeddable, which is a rare feat among the OS-specific backends.
+in all tests and is fully embeddable, which is a rare feat among the
+OS-specific backends (I vastly prefer correctness over speed hacks).
+.Sp
+This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
+\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
 .ie n .IP """EVBACKEND_ALL""" 4
 .el .IP "\f(CWEVBACKEND_ALL\fR" 4
 .IX Item "EVBACKEND_ALL"
 Try all backends (even potentially broken ones that wouldn't be tried
 with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
 .Sp
 If one or more of these are or'ed into the flags value, then only these
 backends will be tried (in the reverse order as listed here). If none are
 specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried.
 .Sp
-The most typical usage is like this:
+Example: This is the most typical usage.
 .Sp
 .Vb 2
 \&   if (!ev_default_loop (0))
 \&     fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
 .Ve
 .Sp
-Restrict libev to the select and poll backends, and do not allow
+Example: Restrict libev to the select and poll backends, and do not allow
 environment settings to be taken into account:
 .Sp
 .Vb 1
 \&   ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
 .Ve
 .Sp
-Use whatever libev has to offer, but make sure that kqueue is used if
+Example: Use whatever libev has to offer, but make sure that kqueue is
-available (warning, breaks stuff, best use only with your own private
+used if available (warning, breaks stuff, best use only with your own
-event loop and only if you know the \s-1OS\s0 supports your types of fds):
+private event loop and only if you know the \s-1OS\s0 supports your types of
+fds):
 .Sp
 .Vb 1
 \&   ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
 .Ve
 .RE
 responsibility to either stop all watchers cleanly yourself \fIbefore\fR
 calling this function, or cope with the fact afterwards (which is usually
 the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
 for example).
 .Sp
-Note that certain global state, such as signal state, will not be freed by
+Note that certain global state, such as signal state (and installed signal
-this function, and related watchers (such as signal and child watchers)
+handlers), will not be freed by this function, and related watchers (such
-would need to be stopped manually.
+as signal and child watchers) would need to be stopped manually.
 .Sp
 In general it is not advisable to call this function except in the
 rare occasion where you really need to free e.g. the signal handling
 pipe fds. If you need dynamically allocated loops it is better to use
 \&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
 .Ve
 .IP "ev_loop_fork (loop)" 4
 .IX Item "ev_loop_fork (loop)"
 Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
 \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
-after fork, and how you do this is entirely your own problem.
+after fork that you want to re-use in the child, and how you do this is
+entirely your own problem.
 .IP "int ev_is_default_loop (loop)" 4
 .IX Item "int ev_is_default_loop (loop)"
-Returns true when the given loop actually is the default loop, false otherwise.
+Returns true when the given loop is, in fact, the default loop, and false
+otherwise.
 .IP "unsigned int ev_loop_count (loop)" 4
 .IX Item "unsigned int ev_loop_count (loop)"
 Returns the count of loop iterations for the loop, which is identical to
 the number of times libev did poll for new events. It starts at \f(CW0\fR and
 happily wraps around with enough iterations.
 .Sp
 This value can sometimes be useful as a generation counter of sorts (it
 \&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
 \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
+.IP "unsigned int ev_loop_depth (loop)" 4
+.IX Item "unsigned int ev_loop_depth (loop)"
+Returns the number of times \f(CW\*(C`ev_loop\*(C'\fR was entered minus the number of
+times \f(CW\*(C`ev_loop\*(C'\fR was exited, in other words, the recursion depth.
+.Sp
+Outside \f(CW\*(C`ev_loop\*(C'\fR, this number is zero. In a callback, this number is
+\&\f(CW1\fR, unless \f(CW\*(C`ev_loop\*(C'\fR was invoked recursively (or from another thread),
+in which case it is higher.
+.Sp
+Leaving \f(CW\*(C`ev_loop\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread
+etc.), doesn't count as exit.
 .IP "unsigned int ev_backend (loop)" 4
 .IX Item "unsigned int ev_backend (loop)"
 Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
 use.
 .IP "ev_tstamp ev_now (loop)" 4
 Returns the current \*(L"event loop time\*(R", which is the time the event loop
 received events and started processing them. This timestamp does not
 change as long as callbacks are being processed, and this is also the base
 time used for relative timers. You can treat it as the timestamp of the
 event occurring (or more correctly, libev finding out about it).
+.IP "ev_now_update (loop)" 4
+.IX Item "ev_now_update (loop)"
+Establishes the current time by querying the kernel, updating the time
+returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and
+is usually done automatically within \f(CW\*(C`ev_loop ()\*(C'\fR.
+.Sp
+This function is rarely useful, but when some event callback runs for a
+very long time without entering the event loop, updating libev's idea of
+the current time is a good idea.
+.Sp
+See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section.
+.IP "ev_suspend (loop)" 4
+.IX Item "ev_suspend (loop)"
+.PD 0
+.IP "ev_resume (loop)" 4
+.IX Item "ev_resume (loop)"
+.PD
+These two functions suspend and resume a loop, for use when the loop is
+not used for a while and timeouts should not be processed.
+.Sp
+A typical use case would be an interactive program such as a game:  When
+the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it
+would be best to handle timeouts as if no time had actually passed while
+the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR
+in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling
+\&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing.
+.Sp
+Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend
+between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers
+will be rescheduled (that is, they will lose any events that would have
+occured while suspended).
+.Sp
+After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the
+given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR
+without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR.
+.Sp
+Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the
+event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR).
 .IP "ev_loop (loop, int flags)" 4
 .IX Item "ev_loop (loop, int flags)"
 Finally, this is it, the event handler. This function usually is called
 after you initialised all your watchers and you want to start handling
 events.
 If the flags argument is specified as \f(CW0\fR, it will not return until
 either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
 .Sp
 Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
 relying on all watchers to be stopped when deciding when a program has
-finished (especially in interactive programs), but having a program that
+finished (especially in interactive programs), but having a program
-automatically loops as long as it has to and no longer by virtue of
+that automatically loops as long as it has to and no longer by virtue
-relying on its watchers stopping correctly is a thing of beauty.
+of relying on its watchers stopping correctly, that is truly a thing of
+beauty.
 .Sp
 A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
-those events and any outstanding ones, but will not block your process in
+those events and any already outstanding ones, but will not block your
-case there are no events and will return after one iteration of the loop.
+process in case there are no events and will return after one iteration of
+the loop.
 .Sp
 A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
-necessary) and will handle those and any outstanding ones. It will block
+necessary) and will handle those and any already outstanding ones. It
-your process until at least one new event arrives, and will return after
+will block your process until at least one new event arrives (which could
-one iteration of the loop. This is useful if you are waiting for some
+be an event internal to libev itself, so there is no guarantee that a
-external event in conjunction with something not expressible using other
+user-registered callback will be called), and will return after one
+iteration of the loop.
+.Sp
+This is useful if you are waiting for some external event in conjunction
+with something not expressible using other libev watchers (i.e. "roll your
-libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
+own \f(CW\*(C`ev_loop\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
 usually a better approach for this kind of thing.
 .Sp
 Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
 .Sp
 .Vb 10
 \&   \- Before the first iteration, call any pending watchers.
 \&   * If EVFLAG_FORKCHECK was used, check for a fork.
-\&   \- If a fork was detected, queue and call all fork watchers.
+\&   \- If a fork was detected (by any means), queue and call all fork watchers.
 \&   \- Queue and call all prepare watchers.
-\&   \- If we have been forked, recreate the kernel state.
+\&   \- If we have been forked, detach and recreate the kernel state
+\&     as to not disturb the other process.
 \&   \- Update the kernel state with all outstanding changes.
-\&   \- Update the "event loop time".
+\&   \- Update the "event loop time" (ev_now ()).
 \&   \- Calculate for how long to sleep or block, if at all
 \&     (active idle watchers, EVLOOP_NONBLOCK or not having
 \&     any active watchers at all will result in not sleeping).
 \&   \- Sleep if the I/O and timer collect interval say so.
 \&   \- Block the process, waiting for any events.
 \&   \- Queue all outstanding I/O (fd) events.
-\&   \- Update the "event loop time" and do time jump handling.
+\&   \- Update the "event loop time" (ev_now ()), and do time jump adjustments.
-\&   \- Queue all outstanding timers.
+\&   \- Queue all expired timers.
-\&   \- Queue all outstanding periodics.
+\&   \- Queue all expired periodics.
-\&   \- If no events are pending now, queue all idle watchers.
+\&   \- Unless any events are pending now, queue all idle watchers.
 \&   \- Queue all check watchers.
 \&   \- Call all queued watchers in reverse order (i.e. check watchers first).
 \&     Signals and child watchers are implemented as I/O watchers, and will
 \&     be handled here by queueing them when their watcher gets executed.
 \&   \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
 .Sp
 .Vb 4
 \&   ... queue jobs here, make sure they register event watchers as long
 \&   ... as they still have work to do (even an idle watcher will do..)
 \&   ev_loop (my_loop, 0);
-\&   ... jobs done. yeah!
+\&   ... jobs done or somebody called unloop. yeah!
 .Ve
 .IP "ev_unloop (loop, how)" 4
 .IX Item "ev_unloop (loop, how)"
 Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
 has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
 \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or
 \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return.
 .Sp
 This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again.
+.Sp
+It is safe to call \f(CW\*(C`ev_unloop\*(C'\fR from otuside any \f(CW\*(C`ev_loop\*(C'\fR calls.
 .IP "ev_ref (loop)" 4
 .IX Item "ev_ref (loop)"
 .PD 0
 .IP "ev_unref (loop)" 4
 .IX Item "ev_unref (loop)"
 .PD
 Ref/unref can be used to add or remove a reference count on the event
 loop: Every watcher keeps one reference, and as long as the reference
-count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have
+count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own.
+.Sp
-a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from
+If you have a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR
-returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For
+from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\fR before
+stopping it.
+.Sp
-example, libev itself uses this for its internal signal pipe: It is not
+As an example, libev itself uses this for its internal signal pipe: It
-visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
+is not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from
-no event watchers registered by it are active. It is also an excellent
+exiting if no event watchers registered by it are active. It is also an
-way to do this for generic recurring timers or from within third-party
+excellent way to do this for generic recurring timers or from within
-libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR
+third-party libraries. Just remember to \fIunref after start\fR and \fIref
-(but only if the watcher wasn't active before, or was active before,
+before stop\fR (but only if the watcher wasn't active before, or was active
-respectively).
+before, respectively. Note also that libev might stop watchers itself
+(e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR
+in the callback).
 .Sp
 Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
 running when nothing else is active.
 .Sp
 .Vb 4
-\&   struct ev_signal exitsig;
+\&   ev_signal exitsig;
 \&   ev_signal_init (&exitsig, sig_cb, SIGINT);
 \&   ev_signal_start (loop, &exitsig);
 \&   evf_unref (loop);
 .Ve
 .Sp
 .PD 0
 .IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
 .IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
 .PD
 These advanced functions influence the time that libev will spend waiting
-for events. Both are by default \f(CW0\fR, meaning that libev will try to
+for events. Both time intervals are by default \f(CW0\fR, meaning that libev
-invoke timer/periodic callbacks and I/O callbacks with minimum latency.
+will try to invoke timer/periodic callbacks and I/O callbacks with minimum
+latency.
 .Sp
 Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
-allows libev to delay invocation of I/O and timer/periodic callbacks to
+allows libev to delay invocation of I/O and timer/periodic callbacks
-increase efficiency of loop iterations.
+to increase efficiency of loop iterations (or to increase power-saving
+opportunities).
 .Sp
-The background is that sometimes your program runs just fast enough to
+The idea is that sometimes your program runs just fast enough to handle
-handle one (or very few) event(s) per loop iteration. While this makes
+one (or very few) event(s) per loop iteration. While this makes the
-the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
+program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
 events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
 overhead for the actual polling but can deliver many events at once.
 .Sp
 By setting a higher \fIio collect interval\fR you allow libev to spend more
 time collecting I/O events, so you can handle more events per iteration,
 at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
 \&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will
-introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations.
+introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The
+sleep time ensures that libev will not poll for I/O events more often then
+once per this interval, on average.
 .Sp
 Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
 to spend more time collecting timeouts, at the expense of increased
-latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers
+latency/jitter/inexactness (the watcher callback will be called
-will not be affected. Setting this to a non-null value will not introduce
+later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null
-any overhead in libev.
+value will not introduce any overhead in libev.
 .Sp
 Many (busy) programs can usually benefit by setting the I/O collect
 interval to a value near \f(CW0.1\fR or so, which is often enough for
 interactive servers (of course not for games), likewise for timeouts. It
 usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR,
-as this approaches the timing granularity of most systems.
+as this approaches the timing granularity of most systems. Note that if
+you do transactions with the outside world and you can't increase the
+parallelity, then this setting will limit your transaction rate (if you
+need to poll once per transaction and the I/O collect interval is 0.01,
+then you can't do more than 100 transations per second).
+.Sp
+Setting the \fItimeout collect interval\fR can improve the opportunity for
+saving power, as the program will \*(L"bundle\*(R" timer callback invocations that
+are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of
+times the process sleeps and wakes up again. Another useful technique to
+reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure
+they fire on, say, one-second boundaries only.
+.Sp
+Example: we only need 0.1s timeout granularity, and we wish not to poll
+more often than 100 times per second:
+.Sp
+.Vb 2
+\&   ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
+\&   ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
+.Ve
+.IP "ev_invoke_pending (loop)" 4
+.IX Item "ev_invoke_pending (loop)"
+This call will simply invoke all pending watchers while resetting their
+pending state. Normally, \f(CW\*(C`ev_loop\*(C'\fR does this automatically when required,
+but when overriding the invoke callback this call comes handy.
+.IP "int ev_pending_count (loop)" 4
+.IX Item "int ev_pending_count (loop)"
+Returns the number of pending watchers \- zero indicates that no watchers
+are pending.
+.IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4
+.IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))"
+This overrides the invoke pending functionality of the loop: Instead of
+invoking all pending watchers when there are any, \f(CW\*(C`ev_loop\*(C'\fR will call
+this callback instead. This is useful, for example, when you want to
+invoke the actual watchers inside another context (another thread etc.).
+.Sp
+If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new
+callback.
+.IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0), void (*acquire)(\s-1EV_P\s0))" 4
+.IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))"
+Sometimes you want to share the same loop between multiple threads. This
+can be done relatively simply by putting mutex_lock/unlock calls around
+each call to a libev function.
+.Sp
+However, \f(CW\*(C`ev_loop\*(C'\fR can run an indefinite time, so it is not feasible to
+wait for it to return. One way around this is to wake up the loop via
+\&\f(CW\*(C`ev_unloop\*(C'\fR and \f(CW\*(C`av_async_send\*(C'\fR, another way is to set these \fIrelease\fR
+and \fIacquire\fR callbacks on the loop.
+.Sp
+When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is
+suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just
+afterwards.
+.Sp
+Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and
+\&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again.
+.Sp
+While event loop modifications are allowed between invocations of
+\&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no
+modifications done will affect the event loop, i.e. adding watchers will
+have no effect on the set of file descriptors being watched, or the time
+waited. USe an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_loop\*(C'\fR when you want it
+to take note of any changes you made.
+.Sp
+In theory, threads executing \f(CW\*(C`ev_loop\*(C'\fR will be async-cancel safe between
+invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR.
+.Sp
+See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this
+document.
+.IP "ev_set_userdata (loop, void *data)" 4
+.IX Item "ev_set_userdata (loop, void *data)"
+.PD 0
+.IP "ev_userdata (loop)" 4
+.IX Item "ev_userdata (loop)"
+.PD
+Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When
+\&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns
+\&\f(CW0.\fR
+.Sp
+These two functions can be used to associate arbitrary data with a loop,
+and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and
+\&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for
+any other purpose as well.
 .IP "ev_loop_verify (loop)" 4
 .IX Item "ev_loop_verify (loop)"
 This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been
-compiled in. It tries to go through all internal structures and checks
+compiled in, which is the default for non-minimal builds. It tries to go
-them for validity. If anything is found to be inconsistent, it will print
+through all internal structures and checks them for validity. If anything
-an error message to standard error and call \f(CW\*(C`abort ()\*(C'\fR.
+is found to be inconsistent, it will print an error message to standard
+error and call \f(CW\*(C`abort ()\*(C'\fR.
 .Sp
 This can be used to catch bugs inside libev itself: under normal
 circumstances, this function will never abort as of course libev keeps its
 data structures consistent.
 .SH "ANATOMY OF A WATCHER"
 .IX Header "ANATOMY OF A WATCHER"
+In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the
+watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer
+watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers.
+.PP
 A watcher is a structure that you create and register to record your
 interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
 become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
 .PP
 .Vb 5
-\&   static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+\&   static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
 \&   {
 \&     ev_io_stop (w);
 \&     ev_unloop (loop, EVUNLOOP_ALL);
 \&   }
 \&
 \&   struct ev_loop *loop = ev_default_loop (0);
+\&
-\&   struct ev_io stdin_watcher;
+\&   ev_io stdin_watcher;
+\&
 \&   ev_init (&stdin_watcher, my_cb);
 \&   ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
 \&   ev_io_start (loop, &stdin_watcher);
+\&
 \&   ev_loop (loop, 0);
 .Ve
 .PP
 As you can see, you are responsible for allocating the memory for your
-watcher structures (and it is usually a bad idea to do this on the stack,
+watcher structures (and it is \fIusually\fR a bad idea to do this on the
-although this can sometimes be quite valid).
+stack).
+.PP
+Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR
+or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs).
 .PP
 Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init
 (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This
 callback gets invoked each time the event occurs (or, in the case of I/O
 watchers, each time the event loop detects that the file descriptor given
 is readable and/or writable).
 .PP
-Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro
+Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR
-with arguments specific to this watcher type. There is also a macro
+macro to configure it, with arguments specific to the watcher type. There
-to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init
+is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR.
-(watcher *, callback, ...)\*(C'\fR.
 .PP
 To make the watcher actually watch out for events, you have to start it
-with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher
+with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher
 *)\*(C'\fR), and you can stop watching for events at any time by calling the
-corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
+corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR.
 .PP
 As long as your watcher is active (has been started but not stopped) you
 must not touch the values stored in it. Most specifically you must never
-reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
+reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
 .PP
 Each and every callback receives the event loop pointer as first, the
 registered watcher structure as second, and a bitset of received events as
 third argument.
 .PP
 \&\f(CW\*(C`ev_fork\*(C'\fR).
 .ie n .IP """EV_ASYNC""" 4
 .el .IP "\f(CWEV_ASYNC\fR" 4
 .IX Item "EV_ASYNC"
 The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR).
+.ie n .IP """EV_CUSTOM""" 4
+.el .IP "\f(CWEV_CUSTOM\fR" 4
+.IX Item "EV_CUSTOM"
+Not ever sent (or otherwise used) by libev itself, but can be freely used
+by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR).
 .ie n .IP """EV_ERROR""" 4
 .el .IP "\f(CWEV_ERROR\fR" 4
 .IX Item "EV_ERROR"
 An unspecified error has occurred, the watcher has been stopped. This might
 happen because the watcher could not be properly started because libev
 ran out of memory, a file descriptor was found to be closed or any other
+problem. Libev considers these application bugs.
+.Sp
-problem. You best act on it by reporting the problem and somehow coping
+You best act on it by reporting the problem and somehow coping with the
-with the watcher being stopped.
+watcher being stopped. Note that well-written programs should not receive
+an error ever, so when your watcher receives it, this usually indicates a
+bug in your program.
 .Sp
-Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
+Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for
-for example it might indicate that a fd is readable or writable, and if
+example it might indicate that a fd is readable or writable, and if your
-your callbacks is well-written it can just attempt the operation and cope
+callbacks is well-written it can just attempt the operation and cope with
-with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded
+the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded
-programs, though, so beware.
+programs, though, as the fd could already be closed and reused for another
+thing, so beware.
-.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
+.SS "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
 .IX Subsection "GENERIC WATCHER FUNCTIONS"
-In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
-e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
 .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
 .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
 .IX Item "ev_init (ev_TYPE *watcher, callback)"
 This macro initialises the generic portion of a watcher. The contents
 of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
 which rolls both calls into one.
 .Sp
 You can reinitialise a watcher at any time as long as it has been stopped
 (or never started) and there are no pending events outstanding.
 .Sp
-The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
+The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher,
 int revents)\*(C'\fR.
+.Sp
+Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps.
+.Sp
+.Vb 3
+\&   ev_io w;
+\&   ev_init (&w, my_cb);
+\&   ev_io_set (&w, STDIN_FILENO, EV_READ);
+.Ve
 .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
 .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
 .IX Item "ev_TYPE_set (ev_TYPE *, [args])"
 This macro initialises the type-specific parts of a watcher. You need to
 call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
 macro on a watcher that is active (it can be pending, however, which is a
 difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
 .Sp
 Although some watcher types do not have type-specific arguments
 (e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
+.Sp
+See \f(CW\*(C`ev_init\*(C'\fR, above, for an example.
 .ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
 .el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
 .IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
 This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
 calls into a single call. This is the most convenient method to initialise
 a watcher. The same limitations apply, of course.
+.Sp
+Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step.
+.Sp
+.Vb 1
+\&   ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
+.Ve
 .ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
 .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
 .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
 Starts (activates) the given watcher. Only active watchers will receive
 events. If the watcher is already active nothing will happen.
+.Sp
+Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this
+whole section.
+.Sp
+.Vb 1
+\&   ev_io_start (EV_DEFAULT_UC, &w);
+.Ve
 .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
 .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
 .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
-Stops the given watcher again (if active) and clears the pending
+Stops the given watcher if active, and clears the pending status (whether
+the watcher was active or not).
+.Sp
-status. It is possible that stopped watchers are pending (for example,
+It is possible that stopped watchers are pending \- for example,
-non-repeating timers are being stopped when they become pending), but
+non-repeating timers are being stopped when they become pending \- but
-\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
+calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor
-you want to free or reuse the memory used by the watcher it is therefore a
+pending. If you want to free or reuse the memory used by the watcher it is
-good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
+therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
 .IP "bool ev_is_active (ev_TYPE *watcher)" 4
 .IX Item "bool ev_is_active (ev_TYPE *watcher)"
 Returns a true value iff the watcher is active (i.e. it has been started
 and not yet been stopped). As long as a watcher is active you must not modify
 it.
 integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
 (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
 before watchers with lower priority, but priority will not keep watchers
 from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
 .Sp
-This means that priorities are \fIonly\fR used for ordering callback
-invocation after new events have been received. This is useful, for
-example, to reduce latency after idling, or more often, to bind two
-watchers on the same event and make sure one is called first.
-.Sp
 If you need to suppress invocation when higher priority events are pending
 you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
 .Sp
 You \fImust not\fR change the priority of a watcher as long as it is active or
 pending.
 .Sp
+Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
+fine, as long as you do not mind that the priority value you query might
+or might not have been clamped to the valid range.
+.Sp
 The default priority used by watchers when no priority has been set is
 always \f(CW0\fR, which is supposed to not be too high and not be too low :).
 .Sp
-Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
+See \*(L"\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0\*(R", below, for a more thorough treatment of
-fine, as long as you do not mind that the priority value you query might
+priorities.
-or might not have been adjusted to be within valid range.
 .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
 .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
 Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
 \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
-can deal with that fact.
+can deal with that fact, as both are simply passed through to the
+callback.
 .IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
 .IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
-If the watcher is pending, this function returns clears its pending status
+If the watcher is pending, this function clears its pending status and
-and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
+returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
 watcher isn't pending it does nothing and returns \f(CW0\fR.
+.Sp
+Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its
+callback to be invoked, which can be accomplished with this function.
-.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
+.SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
 .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
 Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
-and read at any time, libev will completely ignore it. This can be used
+and read at any time: libev will completely ignore it. This can be used
 to associate arbitrary data with your watcher. If you need more data and
 don't want to allocate memory and store a pointer to it in that data
 member, you can also \*(L"subclass\*(R" the watcher type and provide your own
 data:
 .PP
 .Vb 7
 \&   struct my_io
 \&   {
-\&     struct ev_io io;
+\&     ev_io io;
 \&     int otherfd;
 \&     void *somedata;
 \&     struct whatever *mostinteresting;
-\&   }
+\&   };
+\&
+\&   ...
+\&   struct my_io w;
+\&   ev_io_init (&w.io, my_cb, fd, EV_READ);
 .Ve
 .PP
 And since your callback will be called with a pointer to the watcher, you
 can cast it back to your own type:
 .PP
 .Vb 5
-\&   static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
+\&   static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
 \&   {
 \&     struct my_io *w = (struct my_io *)w_;
 \&     ...
 \&   }
 .Ve
 .PP
 More interesting and less C\-conformant ways of casting your callback type
 instead have been omitted.
 .PP
-Another common scenario is having some data structure with multiple
+Another common scenario is to use some data structure with multiple
-watchers:
+embedded watchers:
 .PP
 .Vb 6
 \&   struct my_biggy
 \&   {
 \&     int some_data;
 \&     ev_timer t1;
 \&     ev_timer t2;
 \&   }
 .Ve
 .PP
-In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
+In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more
-you need to use \f(CW\*(C`offsetof\*(C'\fR:
+complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct
+in the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies), or you need to use
+some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for real
+programmers):
 .PP
 .Vb 1
 \&   #include <stddef.h>
 \&
 \&   static void
-\&   t1_cb (EV_P_ struct ev_timer *w, int revents)
+\&   t1_cb (EV_P_ ev_timer *w, int revents)
 \&   {
-\&     struct my_biggy big = (struct my_biggy *
+\&     struct my_biggy big = (struct my_biggy *)
 \&       (((char *)w) \- offsetof (struct my_biggy, t1));
 \&   }
 \&
 \&   static void
-\&   t2_cb (EV_P_ struct ev_timer *w, int revents)
+\&   t2_cb (EV_P_ ev_timer *w, int revents)
 \&   {
-\&     struct my_biggy big = (struct my_biggy *
+\&     struct my_biggy big = (struct my_biggy *)
 \&       (((char *)w) \- offsetof (struct my_biggy, t2));
 \&   }
 .Ve
+.SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0"
+.IX Subsection "WATCHER PRIORITY MODELS"
+Many event loops support \fIwatcher priorities\fR, which are usually small
+integers that influence the ordering of event callback invocation
+between watchers in some way, all else being equal.
+.PP
+In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
+description for the more technical details such as the actual priority
+range.
+.PP
+There are two common ways how these these priorities are being interpreted
+by event loops:
+.PP
+In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation
+of lower priority watchers, which means as long as higher priority
+watchers receive events, lower priority watchers are not being invoked.
+.PP
+The less common only-for-ordering model uses priorities solely to order
+callback invocation within a single event loop iteration: Higher priority
+watchers are invoked before lower priority ones, but they all get invoked
+before polling for new events.
+.PP
+Libev uses the second (only-for-ordering) model for all its watchers
+except for idle watchers (which use the lock-out model).
+.PP
+The rationale behind this is that implementing the lock-out model for
+watchers is not well supported by most kernel interfaces, and most event
+libraries will just poll for the same events again and again as long as
+their callbacks have not been executed, which is very inefficient in the
+common case of one high-priority watcher locking out a mass of lower
+priority ones.
+.PP
+Static (ordering) priorities are most useful when you have two or more
+watchers handling the same resource: a typical usage example is having an
+\&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle
+timeouts. Under load, data might be received while the program handles
+other jobs, but since timers normally get invoked first, the timeout
+handler will be executed before checking for data. In that case, giving
+the timer a lower priority than the I/O watcher ensures that I/O will be
+handled first even under adverse conditions (which is usually, but not
+always, what you want).
+.PP
+Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers
+will only be executed when no same or higher priority watchers have
+received events, they can be used to implement the \*(L"lock-out\*(R" model when
+required.
+.PP
+For example, to emulate how many other event libraries handle priorities,
+you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in
+the normal watcher callback, you just start the idle watcher. The real
+processing is done in the idle watcher callback. This causes libev to
+continously poll and process kernel event data for the watcher, but when
+the lock-out case is known to be rare (which in turn is rare :), this is
+workable.
+.PP
+Usually, however, the lock-out model implemented that way will perform
+miserably under the type of load it was designed to handle. In that case,
+it might be preferable to stop the real watcher before starting the
+idle watcher, so the kernel will not have to process the event in case
+the actual processing will be delayed for considerable time.
+.PP
+Here is an example of an I/O watcher that should run at a strictly lower
+priority than the default, and which should only process data when no
+other events are pending:
+.PP
+.Vb 2
+\&   ev_idle idle; // actual processing watcher
+\&   ev_io io;     // actual event watcher
+\&
+\&   static void
+\&   io_cb (EV_P_ ev_io *w, int revents)
+\&   {
+\&     // stop the I/O watcher, we received the event, but
+\&     // are not yet ready to handle it.
+\&     ev_io_stop (EV_A_ w);
+\&
+\&     // start the idle watcher to ahndle the actual event.
+\&     // it will not be executed as long as other watchers
+\&     // with the default priority are receiving events.
+\&     ev_idle_start (EV_A_ &idle);
+\&   }
+\&
+\&   static void
+\&   idle_cb (EV_P_ ev_idle *w, int revents)
+\&   {
+\&     // actual processing
+\&     read (STDIN_FILENO, ...);
+\&
+\&     // have to start the I/O watcher again, as
+\&     // we have handled the event
+\&     ev_io_start (EV_P_ &io);
+\&   }
+\&
+\&   // initialisation
+\&   ev_idle_init (&idle, idle_cb);
+\&   ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
+\&   ev_io_start (EV_DEFAULT_ &io);
+.Ve
+.PP
+In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that
+low-priority connections can not be locked out forever under load. This
+enables your program to keep a lower latency for important connections
+during short periods of high load, while not completely locking out less
+important ones.
 .SH "WATCHER TYPES"
 .IX Header "WATCHER TYPES"
 This section describes each watcher in detail, but will not repeat
 information given in the last section. Any initialisation/set macros,
 functions and members specific to the watcher type are explained.
 watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
 means you can expect it to have some sensible content while the watcher
 is active, but you can also modify it. Modifying it may not do something
 sensible or take immediate effect (or do anything at all), but libev will
 not crash or malfunction in any way.
-.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
+.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
-.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
+.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
 .IX Subsection "ev_io - is this file descriptor readable or writable?"
 I/O watchers check whether a file descriptor is readable or writable
 in each iteration of the event loop, or, more precisely, when reading
 would not block the process and writing would at least be able to write
 some data. This behaviour is called level-triggering because you keep
 In general you can register as many read and/or write event watchers per
 fd as you want (as long as you don't confuse yourself). Setting all file
 descriptors to non-blocking mode is also usually a good idea (but not
 required if you know what you are doing).
 .PP
-If you must do this, then force the use of a known-to-be-good backend
+If you cannot use non-blocking mode, then force the use of a
-(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
+known-to-be-good backend (at the time of this writing, this includes only
-\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
+\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR). The same applies to file
+descriptors for which non-blocking operation makes no sense (such as
+files) \- libev doesn't guarentee any specific behaviour in that case.
 .PP
 Another thing you have to watch out for is that it is quite easy to
 receive \*(L"spurious\*(R" readiness notifications, that is your callback might
 be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
 because there is no data. Not only are some backends known to create a
 lot of those (for example Solaris ports), it is very easy to get into
 this situation even with a relatively standard program structure. Thus
 it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
 \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
 .PP
-If you cannot run the fd in non-blocking mode (for example you should not
+If you cannot run the fd in non-blocking mode (for example you should
-play around with an Xlib connection), then you have to separately re-test
+not play around with an Xlib connection), then you have to separately
-whether a file descriptor is really ready with a known-to-be good interface
+re-test whether a file descriptor is really ready with a known-to-be good
-such as poll (fortunately in our Xlib example, Xlib already does this on
+interface such as poll (fortunately in our Xlib example, Xlib already
-its own, so its quite safe to use).
+does this on its own, so its quite safe to use). Some people additionally
+use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block
+indefinitely.
+.PP
+But really, best use non-blocking mode.
 .PP
 \fIThe special problem of disappearing file descriptors\fR
 .IX Subsection "The special problem of disappearing file descriptors"
 .PP
 Some backends (e.g. kqueue, epoll) need to be told about closing a file
-descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
+descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means,
-such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
+such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file
 descriptor, but when it goes away, the operating system will silently drop
 this interest. If another file descriptor with the same number then is
 registered with libev, there is no efficient way to see that this is, in
 fact, a different file descriptor.
 .PP
 \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
 .PP
 \fIThe special problem of \s-1SIGPIPE\s0\fR
 .IX Subsection "The special problem of SIGPIPE"
 .PP
-While not really specific to libev, it is easy to forget about \s-1SIGPIPE:\s0
+While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR:
-when reading from a pipe whose other end has been closed, your program
+when writing to a pipe whose other end has been closed, your program gets
-gets send a \s-1SIGPIPE\s0, which, by default, aborts your program. For most
+sent a \s-1SIGPIPE\s0, which, by default, aborts your program. For most programs
-programs this is sensible behaviour, for daemons, this is usually
+this is sensible behaviour, for daemons, this is usually undesirable.
-undesirable.
 .PP
 So when you encounter spurious, unexplained daemon exits, make sure you
 ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon
 somewhere, as that would have given you a big clue).
 .PP
 .PD 0
 .IP "ev_io_set (ev_io *, int fd, int events)" 4
 .IX Item "ev_io_set (ev_io *, int fd, int events)"
 .PD
 Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
-receive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
+receive 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
-\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
+\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events.
 .IP "int fd [read\-only]" 4
 .IX Item "int fd [read-only]"
 The file descriptor being watched.
 .IP "int events [read\-only]" 4
 .IX Item "int events [read-only]"
 readable, but only once. Since it is likely line-buffered, you could
 attempt to read a whole line in the callback.
 .PP
 .Vb 6
 \&   static void
-\&   stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+\&   stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
 \&   {
 \&      ev_io_stop (loop, w);
-\&     .. read from stdin here (or from w\->fd) and haqndle any I/O errors
+\&     .. read from stdin here (or from w\->fd) and handle any I/O errors
 \&   }
 \&
 \&   ...
 \&   struct ev_loop *loop = ev_default_init (0);
-\&   struct ev_io stdin_readable;
+\&   ev_io stdin_readable;
 \&   ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
 \&   ev_io_start (loop, &stdin_readable);
 \&   ev_loop (loop, 0);
 .Ve
-.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
+.ie n .SS """ev_timer"" \- relative and optionally repeating timeouts"
-.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
+.el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
 .IX Subsection "ev_timer - relative and optionally repeating timeouts"
 Timer watchers are simple relative timers that generate an event after a
 given time, and optionally repeating in regular intervals after that.
 .PP
 The timers are based on real time, that is, if you register an event that
 times out after an hour and you reset your system clock to January last
-year, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because
+year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because
 detecting time jumps is hard, and some inaccuracies are unavoidable (the
 monotonic clock option helps a lot here).
+.PP
+The callback is guaranteed to be invoked only \fIafter\fR its timeout has
+passed (not \fIat\fR, so on systems with very low-resolution clocks this
+might introduce a small delay). If multiple timers become ready during the
+same loop iteration then the ones with earlier time-out values are invoked
+before ones of the same priority with later time-out values (but this is
+no longer true when a callback calls \f(CW\*(C`ev_loop\*(C'\fR recursively).
+.PP
+\fIBe smart about timeouts\fR
+.IX Subsection "Be smart about timeouts"
+.PP
+Many real-world problems involve some kind of timeout, usually for error
+recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs,
+you want to raise some error after a while.
+.PP
+What follows are some ways to handle this problem, from obvious and
+inefficient to smart and efficient.
+.PP
+In the following, a 60 second activity timeout is assumed \- a timeout that
+gets reset to 60 seconds each time there is activity (e.g. each time some
+data or other life sign was received).
+.IP "1. Use a timer and stop, reinitialise and start it on activity." 4
+.IX Item "1. Use a timer and stop, reinitialise and start it on activity."
+This is the most obvious, but not the most simple way: In the beginning,
+start the watcher:
+.Sp
+.Vb 2
+\&   ev_timer_init (timer, callback, 60., 0.);
+\&   ev_timer_start (loop, timer);
+.Ve
+.Sp
+Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it
+and start it again:
+.Sp
+.Vb 3
+\&   ev_timer_stop (loop, timer);
+\&   ev_timer_set (timer, 60., 0.);
+\&   ev_timer_start (loop, timer);
+.Ve
+.Sp
+This is relatively simple to implement, but means that each time there is
+some activity, libev will first have to remove the timer from its internal
+data structure and then add it again. Libev tries to be fast, but it's
+still not a constant-time operation.
+.ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4
+.el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4
+.IX Item "2. Use a timer and re-start it with ev_timer_again inactivity."
+This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of
+\&\f(CW\*(C`ev_timer_start\*(C'\fR.
+.Sp
+To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value
+of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you
+successfully read or write some data. If you go into an idle state where
+you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR
+the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be.
+.Sp
+That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the
+\&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR
+member and \f(CW\*(C`ev_timer_again\*(C'\fR.
+.Sp
+At start:
+.Sp
+.Vb 3
+\&   ev_init (timer, callback);
+\&   timer\->repeat = 60.;
+\&   ev_timer_again (loop, timer);
+.Ve
+.Sp
+Each time there is some activity:
+.Sp
+.Vb 1
+\&   ev_timer_again (loop, timer);
+.Ve
+.Sp
+It is even possible to change the time-out on the fly, regardless of
+whether the watcher is active or not:
+.Sp
+.Vb 2
+\&   timer\->repeat = 30.;
+\&   ev_timer_again (loop, timer);
+.Ve
+.Sp
+This is slightly more efficient then stopping/starting the timer each time
+you want to modify its timeout value, as libev does not have to completely
+remove and re-insert the timer from/into its internal data structure.
+.Sp
+It is, however, even simpler than the \*(L"obvious\*(R" way to do it.
+.IP "3. Let the timer time out, but then re-arm it as required." 4
+.IX Item "3. Let the timer time out, but then re-arm it as required."
+This method is more tricky, but usually most efficient: Most timeouts are
+relatively long compared to the intervals between other activity \- in
+our example, within 60 seconds, there are usually many I/O events with
+associated activity resets.
+.Sp
+In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone,
+but remember the time of last activity, and check for a real timeout only
+within the callback:
+.Sp
+.Vb 1
+\&   ev_tstamp last_activity; // time of last activity
+\&
+\&   static void
+\&   callback (EV_P_ ev_timer *w, int revents)
+\&   {
+\&     ev_tstamp now     = ev_now (EV_A);
+\&     ev_tstamp timeout = last_activity + 60.;
+\&
+\&     // if last_activity + 60. is older than now, we did time out
+\&     if (timeout < now)
+\&       {
+\&         // timeout occured, take action
+\&       }
+\&     else
+\&       {
+\&         // callback was invoked, but there was some activity, re\-arm
+\&         // the watcher to fire in last_activity + 60, which is
+\&         // guaranteed to be in the future, so "again" is positive:
+\&         w\->repeat = timeout \- now;
+\&         ev_timer_again (EV_A_ w);
+\&       }
+\&   }
+.Ve
+.Sp
+To summarise the callback: first calculate the real timeout (defined
+as \*(L"60 seconds after the last activity\*(R"), then check if that time has
+been reached, which means something \fIdid\fR, in fact, time out. Otherwise
+the callback was invoked too early (\f(CW\*(C`timeout\*(C'\fR is in the future), so
+re-schedule the timer to fire at that future time, to see if maybe we have
+a timeout then.
+.Sp
+Note how \f(CW\*(C`ev_timer_again\*(C'\fR is used, taking advantage of the
+\&\f(CW\*(C`ev_timer_again\*(C'\fR optimisation when the timer is already running.
+.Sp
+This scheme causes more callback invocations (about one every 60 seconds
+minus half the average time between activity), but virtually no calls to
+libev to change the timeout.
+.Sp
+To start the timer, simply initialise the watcher and set \f(CW\*(C`last_activity\*(C'\fR
+to the current time (meaning we just have some activity :), then call the
+callback, which will \*(L"do the right thing\*(R" and start the timer:
+.Sp
+.Vb 3
+\&   ev_init (timer, callback);
+\&   last_activity = ev_now (loop);
+\&   callback (loop, timer, EV_TIMEOUT);
+.Ve
+.Sp
+And when there is some activity, simply store the current time in
+\&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all:
+.Sp
+.Vb 1
+\&   last_actiivty = ev_now (loop);
+.Ve
+.Sp
+This technique is slightly more complex, but in most cases where the
+time-out is unlikely to be triggered, much more efficient.
+.Sp
+Changing the timeout is trivial as well (if it isn't hard-coded in the
+callback :) \- just change the timeout and invoke the callback, which will
+fix things for you.
+.IP "4. Wee, just use a double-linked list for your timeouts." 4
+.IX Item "4. Wee, just use a double-linked list for your timeouts."
+If there is not one request, but many thousands (millions...), all
+employing some kind of timeout with the same timeout value, then one can
+do even better:
+.Sp
+When starting the timeout, calculate the timeout value and put the timeout
+at the \fIend\fR of the list.
+.Sp
+Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of
+the list is expected to fire (for example, using the technique #3).
+.Sp
+When there is some activity, remove the timer from the list, recalculate
+the timeout, append it to the end of the list again, and make sure to
+update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list.
+.Sp
+This way, one can manage an unlimited number of timeouts in O(1) time for
+starting, stopping and updating the timers, at the expense of a major
+complication, and having to use a constant timeout. The constant timeout
+ensures that the list stays sorted.
+.PP
+So which method the best?
+.PP
+Method #2 is a simple no-brain-required solution that is adequate in most
+situations. Method #3 requires a bit more thinking, but handles many cases
+better, and isn't very complicated either. In most case, choosing either
+one is fine, with #3 being better in typical situations.
+.PP
+Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
+rather complicated, but extremely efficient, something that really pays
+off after the first million or so of active timers, i.e. it's usually
+overkill :)
+.PP
+\fIThe special problem of time updates\fR
+.IX Subsection "The special problem of time updates"
+.PP
+Establishing the current time is a costly operation (it usually takes at
+least two system calls): \s-1EV\s0 therefore updates its idea of the current
+time only before and after \f(CW\*(C`ev_loop\*(C'\fR collects new events, which causes a
+growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling
+lots of events in one iteration.
 .PP
 The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
 time. This is usually the right thing as this timestamp refers to the time
 of the event triggering whatever timeout you are modifying/starting. If
-you suspect event processing to be delayed and you \fIneed\fR to base the timeout
+you suspect event processing to be delayed and you \fIneed\fR to base the
-on the current time, use something like this to adjust for this:
+timeout on the current time, use something like this to adjust for this:
 .PP
 .Vb 1
 \&   ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.);
 .Ve
 .PP
-The callback is guaranteed to be invoked only after its timeout has passed,
+If the event loop is suspended for a long time, you can also force an
-but if multiple timers become ready during the same loop iteration then
+update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update
-order of execution is undefined.
+()\*(C'\fR.
+.PP
+\fIThe special problems of suspended animation\fR
+.IX Subsection "The special problems of suspended animation"
+.PP
+When you leave the server world it is quite customary to hit machines that
+can suspend/hibernate \- what happens to the clocks during such a suspend?
+.PP
+Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
+all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue
+to run until the system is suspended, but they will not advance while the
+system is suspended. That means, on resume, it will be as if the program
+was frozen for a few seconds, but the suspend time will not be counted
+towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time
+clock advanced as expected, but if it is used as sole clocksource, then a
+long suspend would be detected as a time jump by libev, and timers would
+be adjusted accordingly.
+.PP
+I would not be surprised to see different behaviour in different between
+operating systems, \s-1OS\s0 versions or even different hardware.
+.PP
+The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a
+time jump in the monotonic clocks and the realtime clock. If the program
+is suspended for a very long time, and monotonic clock sources are in use,
+then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time
+will be counted towards the timers. When no monotonic clock source is in
+use, then libev will again assume a timejump and adjust accordingly.
+.PP
+It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR
+and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get
+deterministic behaviour in this case (you can do nothing against
+\&\f(CW\*(C`SIGSTOP\*(C'\fR).
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
 .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
 If the timer is started but non-repeating, stop it (as if it timed out).
 .Sp
 If the timer is repeating, either start it if necessary (with the
 \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
 .Sp
-This sounds a bit complicated, but here is a useful and typical
+This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a
-example: Imagine you have a \s-1TCP\s0 connection and you want a so-called idle
+usage example.
-timeout, that is, you want to be called when there have been, say, 60
+.IP "ev_timer_remaining (loop, ev_timer *)" 4
-seconds of inactivity on the socket. The easiest way to do this is to
+.IX Item "ev_timer_remaining (loop, ev_timer *)"
-configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
+Returns the remaining time until a timer fires. If the timer is active,
-\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
+then this time is relative to the current event loop time, otherwise it's
-you go into an idle state where you do not expect data to travel on the
+the timeout value currently configured.
-socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
-automatically restart it if need be.
 .Sp
-That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
+That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns
-altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
+\&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remain\*(C'\fR
-.Sp
+will return \f(CW4\fR. When the timer expires and is restarted, it will return
-.Vb 8
+roughly \f(CW7\fR (likely slightly less as callback invocation takes some time,
-\&   ev_timer_init (timer, callback, 0., 5.);
+too), and so on.
-\&   ev_timer_again (loop, timer);
-\&   ...
-\&   timer\->again = 17.;
-\&   ev_timer_again (loop, timer);
-\&   ...
-\&   timer\->again = 10.;
-\&   ev_timer_again (loop, timer);
-.Ve
-.Sp
-This is more slightly efficient then stopping/starting the timer each time
-you want to modify its timeout value.
 .IP "ev_tstamp repeat [read\-write]" 4
 .IX Item "ev_tstamp repeat [read-write]"
 The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
-or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
+or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any),
 which is also when any modifications are taken into account.
 .PP
 \fIExamples\fR
 .IX Subsection "Examples"
 .PP
 Example: Create a timer that fires after 60 seconds.
 .PP
 .Vb 5
 \&   static void
-\&   one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+\&   one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
 \&   {
 \&     .. one minute over, w is actually stopped right here
 \&   }
 \&
-\&   struct ev_timer mytimer;
+\&   ev_timer mytimer;
 \&   ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
 \&   ev_timer_start (loop, &mytimer);
 .Ve
 .PP
 Example: Create a timeout timer that times out after 10 seconds of
 inactivity.
 .PP
 .Vb 5
 \&   static void
-\&   timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+\&   timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
 \&   {
 \&     .. ten seconds without any activity
 \&   }
 \&
-\&   struct ev_timer mytimer;
+\&   ev_timer mytimer;
 \&   ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
 \&   ev_timer_again (&mytimer); /* start timer */
 \&   ev_loop (loop, 0);
 \&
 \&   // and in some piece of code that gets executed on any "activity":
 \&   // reset the timeout to start ticking again at 10 seconds
 \&   ev_timer_again (&mytimer);
 .Ve
-.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
+.ie n .SS """ev_periodic"" \- to cron or not to cron?"
-.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
+.el .SS "\f(CWev_periodic\fP \- to cron or not to cron?"
 .IX Subsection "ev_periodic - to cron or not to cron?"
 Periodic watchers are also timers of a kind, but they are very versatile
 (and unfortunately a bit complex).
 .PP
-Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
+Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or
-but on wall clock time (absolute time). You can tell a periodic watcher
+relative time, the physical time that passes) but on wall clock time
-to trigger after some specific point in time. For example, if you tell a
+(absolute time, the thing you can read on your calender or clock). The
-periodic watcher to trigger in 10 seconds (by specifying e.g. \f(CW\*(C`ev_now ()
+difference is that wall clock time can run faster or slower than real
-+ 10.\*(C'\fR, that is, an absolute time not a delay) and then reset your system
+time, and time jumps are not uncommon (e.g. when you adjust your
-clock to January of the previous year, then it will take more than year
+wrist-watch).
-to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would still trigger
-roughly 10 seconds later as it uses a relative timeout).
 .PP
+You can tell a periodic watcher to trigger after some specific point
+in time: for example, if you tell a periodic watcher to trigger \*(L"in 10
+seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time
+not a delay) and then reset your system clock to January of the previous
+year, then it will take a year or more to trigger the event (unlike an
+\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting
+it, as it uses a relative timeout).
+.PP
-\&\f(CW\*(C`ev_periodic\*(C'\fRs can also be used to implement vastly more complex timers,
+\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex
-such as triggering an event on each \*(L"midnight, local time\*(R", or other
+timers, such as triggering an event on each \*(L"midnight, local time\*(R", or
-complicated, rules.
+other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as
+those cannot react to time jumps.
 .PP
 As with timers, the callback is guaranteed to be invoked only when the
-time (\f(CW\*(C`at\*(C'\fR) has passed, but if multiple periodic timers become ready
+point in time where it is supposed to trigger has passed. If multiple
-during the same loop iteration then order of execution is undefined.
+timers become ready during the same loop iteration then the ones with
+earlier time-out values are invoked before ones with later time-out values
+(but this is no longer true when a callback calls \f(CW\*(C`ev_loop\*(C'\fR recursively).
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
-.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
+.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
-.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
+.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
 .PD 0
-.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
+.IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4
-.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
+.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)"
 .PD
-Lots of arguments, lets sort it out... There are basically three modes of
+Lots of arguments, let's sort it out... There are basically three modes of
-operation, and we will explain them from simplest to complex:
+operation, and we will explain them from simplest to most complex:
 .RS 4
 .IP "\(bu" 4
-absolute timer (at = time, interval = reschedule_cb = 0)
+absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
 .Sp
 In this configuration the watcher triggers an event after the wall clock
-time \f(CW\*(C`at\*(C'\fR has passed and doesn't repeat. It will not adjust when a time
+time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a
-jump occurs, that is, if it is to be run at January 1st 2011 then it will
+time jump occurs, that is, if it is to be run at January 1st 2011 then it
-run when the system time reaches or surpasses this time.
+will be stopped and invoked when the system clock reaches or surpasses
+this point in time.
 .IP "\(bu" 4
-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
+repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
 .Sp
 In this mode the watcher will always be scheduled to time out at the next
-\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
+\&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be
-and then repeat, regardless of any time jumps.
+negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR
+argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods.
 .Sp
-This can be used to create timers that do not drift with respect to system
+This can be used to create timers that do not drift with respect to the
-time, for example, here is a \f(CW\*(C`ev_periodic\*(C'\fR that triggers each hour, on
+system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each
-the hour:
+hour, on the hour (with respect to \s-1UTC\s0):
 .Sp
 .Vb 1
 \&   ev_periodic_set (&periodic, 0., 3600., 0);
 .Ve
 .Sp
 full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
 by 3600.
 .Sp
 Another way to think about it (for the mathematically inclined) is that
 \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
-time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
+time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps.
 .Sp
-For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
+For numerical stability it is preferable that the \f(CW\*(C`offset\*(C'\fR value is near
 \&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
 this value, and in fact is often specified as zero.
 .Sp
 Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0
 speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability
 will of course deteriorate. Libev itself tries to be exact to be about one
 millisecond (if the \s-1OS\s0 supports it and the machine is fast enough).
 .IP "\(bu" 4
-manual reschedule mode (at and interval ignored, reschedule_cb = callback)
+manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
 .Sp
-In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
+In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being
 ignored. Instead, each time the periodic watcher gets scheduled, the
 reschedule callback will be called with the watcher as first, and the
 current time as second argument.
 .Sp
-\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
+\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, ever,
-ever, or make \s-1ANY\s0 event loop modifications whatsoever\fR.
+or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly
+allowed by documentation here\fR.
 .Sp
 If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop
 it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the
 only event loop modification you are allowed to do).
 .Sp
-The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic
+The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic
 *w, ev_tstamp now)\*(C'\fR, e.g.:
 .Sp
-.Vb 4
+.Vb 5
+\&   static ev_tstamp
-\&   static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
+\&   my_rescheduler (ev_periodic *w, ev_tstamp now)
 \&   {
 \&     return now + 60.;
 \&   }
 .Ve
 .Sp
 when you changed some parameters or the reschedule callback would return
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
 .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4
 .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)"
-When active, returns the absolute time that the watcher is supposed to
+When active, returns the absolute time that the watcher is supposed
-trigger next.
+to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to
+\&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual
+rescheduling modes.
 .IP "ev_tstamp offset [read\-write]" 4
 .IX Item "ev_tstamp offset [read-write]"
 When repeating, this contains the offset value, otherwise this is the
-absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
+absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR,
+although libev might modify this value for better numerical stability).
 .Sp
 Can be modified any time, but changes only take effect when the periodic
 timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
 .IP "ev_tstamp interval [read\-write]" 4
 .IX Item "ev_tstamp interval [read-write]"
 The current interval value. Can be modified any time, but changes only
 take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
 called.
-.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
+.IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4
-.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
+.IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]"
 The current reschedule callback, or \f(CW0\fR, if this functionality is
 switched off. Can be changed any time, but changes only take effect when
 the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
 .PP
 \fIExamples\fR
 .IX Subsection "Examples"
 .PP
 Example: Call a callback every hour, or, more precisely, whenever the
-system clock is divisible by 3600. The callback invocation times have
+system time is divisible by 3600. The callback invocation times have
 potentially a lot of jitter, but good long-term stability.
 .PP
 .Vb 5
 \&   static void
-\&   clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+\&   clock_cb (struct ev_loop *loop, ev_io *w, int revents)
 \&   {
 \&     ... its now a full hour (UTC, or TAI or whatever your clock follows)
 \&   }
 \&
-\&   struct ev_periodic hourly_tick;
+\&   ev_periodic hourly_tick;
 \&   ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
 \&   ev_periodic_start (loop, &hourly_tick);
 .Ve
 .PP
 Example: The same as above, but use a reschedule callback to do it:
 .PP
 .Vb 1
 \&   #include <math.h>
 \&
 \&   static ev_tstamp
-\&   my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
+\&   my_scheduler_cb (ev_periodic *w, ev_tstamp now)
 \&   {
-\&     return fmod (now, 3600.) + 3600.;
+\&     return now + (3600. \- fmod (now, 3600.));
 \&   }
 \&
 \&   ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
 .Ve
 .PP
 Example: Call a callback every hour, starting now:
 .PP
 .Vb 4
-\&   struct ev_periodic hourly_tick;
+\&   ev_periodic hourly_tick;
 \&   ev_periodic_init (&hourly_tick, clock_cb,
 \&                     fmod (ev_now (loop), 3600.), 3600., 0);
 \&   ev_periodic_start (loop, &hourly_tick);
 .Ve
-.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
+.ie n .SS """ev_signal"" \- signal me when a signal gets signalled!"
-.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
+.el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
 .IX Subsection "ev_signal - signal me when a signal gets signalled!"
 Signal watchers will trigger an event when the process receives a specific
 signal one or more times. Even though signals are very asynchronous, libev
 will try it's best to deliver signals synchronously, i.e. as part of the
 normal event processing, like any other event.
 .PP
+If you want signals asynchronously, just use \f(CW\*(C`sigaction\*(C'\fR as you would
+do without libev and forget about sharing the signal. You can even use
+\&\f(CW\*(C`ev_async\*(C'\fR from a signal handler to synchronously wake up an event loop.
+.PP
 You can configure as many watchers as you like per signal. Only when the
-first watcher gets started will libev actually register a signal watcher
+first watcher gets started will libev actually register a signal handler
-with the kernel (thus it coexists with your own signal handlers as long
+with the kernel (thus it coexists with your own signal handlers as long as
-as you don't register any with libev). Similarly, when the last signal
+you don't register any with libev for the same signal). Similarly, when
-watcher for a signal is stopped libev will reset the signal handler to
+the last signal watcher for a signal is stopped, libev will reset the
-\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
+signal handler to \s-1SIG_DFL\s0 (regardless of what it was set to before).
 .PP
 If possible and supported, libev will install its handlers with
 \&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so system calls should not be unduly
 interrupted. If you have a problem with system calls getting interrupted by
 signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock
 The signal the watcher watches out for.
 .PP
 \fIExamples\fR
 .IX Subsection "Examples"
 .PP
-Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
+Example: Try to exit cleanly on \s-1SIGINT\s0.
 .PP
 .Vb 5
 \&   static void
-\&   sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+\&   sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
 \&   {
 \&     ev_unloop (loop, EVUNLOOP_ALL);
 \&   }
 \&
-\&   struct ev_signal signal_watcher;
+\&   ev_signal signal_watcher;
 \&   ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
-\&   ev_signal_start (loop, &sigint_cb);
+\&   ev_signal_start (loop, &signal_watcher);
 .Ve
-.ie n .Sh """ev_child"" \- watch out for process status changes"
+.ie n .SS """ev_child"" \- watch out for process status changes"
-.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
+.el .SS "\f(CWev_child\fP \- watch out for process status changes"
 .IX Subsection "ev_child - watch out for process status changes"
 Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
-some child status changes (most typically when a child of yours dies). It
+some child status changes (most typically when a child of yours dies or
-is permissible to install a child watcher \fIafter\fR the child has been
+exits). It is permissible to install a child watcher \fIafter\fR the child
-forked (which implies it might have already exited), as long as the event
+has been forked (which implies it might have already exited), as long
-loop isn't entered (or is continued from a watcher).
+as the event loop isn't entered (or is continued from a watcher), i.e.,
+forking and then immediately registering a watcher for the child is fine,
+but forking and registering a watcher a few event loop iterations later or
+in the next callback invocation is not.
 .PP
 Only the default event loop is capable of handling signals, and therefore
 you can only register child watchers in the default event loop.
+.PP
+Due to some design glitches inside libev, child watchers will always be
+handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by
+libev)
 .PP
 \fIProcess Interaction\fR
 .IX Subsection "Process Interaction"
 .PP
 Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is
 handler, you can override it easily by installing your own handler for
 \&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the
 default loop never gets destroyed. You are encouraged, however, to use an
 event-based approach to child reaping and thus use libev's support for
 that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely.
+.PP
+\fIStopping the Child Watcher\fR
+.IX Subsection "Stopping the Child Watcher"
+.PP
+Currently, the child watcher never gets stopped, even when the
+child terminates, so normally one needs to stop the watcher in the
+callback. Future versions of libev might stop the watcher automatically
+when a child exit is detected.
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
 .IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
 .PP
 .Vb 1
 \&   ev_child cw;
 \&
 \&   static void
-\&   child_cb (EV_P_ struct ev_child *w, int revents)
+\&   child_cb (EV_P_ ev_child *w, int revents)
 \&   {
 \&     ev_child_stop (EV_A_ w);
 \&     printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus);
 \&   }
 \&
 \&     {
 \&       ev_child_init (&cw, child_cb, pid, 0);
 \&       ev_child_start (EV_DEFAULT_ &cw);
 \&     }
 .Ve
-.ie n .Sh """ev_stat"" \- did the file attributes just change?"
+.ie n .SS """ev_stat"" \- did the file attributes just change?"
-.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
+.el .SS "\f(CWev_stat\fP \- did the file attributes just change?"
 .IX Subsection "ev_stat - did the file attributes just change?"
 This watches a file system path for attribute changes. That is, it calls
-\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
+\&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed)
-compared to the last time, invoking the callback if it did.
+and sees if it changed compared to the last time, invoking the callback if
+it did.
 .PP
 The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
-not exist\*(R" is a status change like any other. The condition \*(L"path does
+not exist\*(R" is a status change like any other. The condition \*(L"path does not
-not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
+exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the
-otherwise always forced to be at least one) and all the other fields of
+\&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at
-the stat buffer having unspecified contents.
+least one) and all the other fields of the stat buffer having unspecified
+contents.
 .PP
-The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
+The path \fImust not\fR end in a slash or contain special components such as
+\&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and
-relative and your working directory changes, the behaviour is undefined.
+your working directory changes, then the behaviour is undefined.
 .PP
-Since there is no standard to do this, the portable implementation simply
+Since there is no portable change notification interface available, the
-calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
+portable implementation simply calls \f(CWstat(2)\fR regularly on the path
-can specify a recommended polling interval for this case. If you specify
+to see if it changed somehow. You can specify a recommended polling
-a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
+interval for this case. If you specify a polling interval of \f(CW0\fR (highly
-unspecified default\fR value will be used (which you can expect to be around
+recommended!) then a \fIsuitable, unspecified default\fR value will be used
-five seconds, although this might change dynamically). Libev will also
+(which you can expect to be around five seconds, although this might
-impose a minimum interval which is currently around \f(CW0.1\fR, but thats
+change dynamically). Libev will also impose a minimum interval which is
-usually overkill.
+currently around \f(CW0.1\fR, but that's usually overkill.
 .PP
 This watcher type is not meant for massive numbers of stat watchers,
 as even with OS-supported change notifications, this can be
 resource-intensive.
 .PP
-At the time of this writing, only the Linux inotify interface is
+At the time of this writing, the only OS-specific interface implemented
-implemented (implementing kqueue support is left as an exercise for the
+is the Linux inotify interface (implementing kqueue support is left as an
-reader, note, however, that the author sees no way of implementing ev_stat
+exercise for the reader. Note, however, that the author sees no way of
-semantics with kqueue). Inotify will be used to give hints only and should
+implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint).
-not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev
-sometimes needs to fall back to regular polling again even with inotify,
-but changes are usually detected immediately, and if the file exists there
-will be no polling.
 .PP
 \fI\s-1ABI\s0 Issues (Largefile Support)\fR
 .IX Subsection "ABI Issues (Largefile Support)"
 .PP
 Libev by default (unless the user overrides this) uses the default
 support disabled by default, you get the 32 bit version of the stat
 structure. When using the library from programs that change the \s-1ABI\s0 to
 use 64 bit file offsets the programs will fail. In that case you have to
 compile libev with the same flags to get binary compatibility. This is
 obviously the case with any flags that change the \s-1ABI\s0, but the problem is
-most noticeably disabled with ev_stat and large file support.
+most noticeably displayed with ev_stat and large file support.
 .PP
 The solution for this is to lobby your distribution maker to make large
 file interfaces available by default (as e.g. FreeBSD does) and not
 optional. Libev cannot simply switch on large file support because it has
 to exchange stat structures with application programs compiled using the
 default compilation environment.
 .PP
-\fIInotify\fR
+\fIInotify and Kqueue\fR
-.IX Subsection "Inotify"
+.IX Subsection "Inotify and Kqueue"
 .PP
-When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only
+When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at
-available on Linux) and present at runtime, it will be used to speed up
+runtime, it will be used to speed up change detection where possible. The
-change detection where possible. The inotify descriptor will be created lazily
+inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR
-when the first \f(CW\*(C`ev_stat\*(C'\fR watcher is being started.
+watcher is being started.
 .PP
 Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers
 except that changes might be detected earlier, and in some cases, to avoid
 making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support
-there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling.
+there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling,
+but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
+many bugs), the path exists (i.e. stat succeeds), and the path resides on
+a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
+xfs are fully working) libev usually gets away without polling.
 .PP
-(There is no support for kqueue, as apparently it cannot be used to
+There is no support for kqueue, as apparently it cannot be used to
 implement this functionality, due to the requirement of having a file
-descriptor open on the object at all times).
+descriptor open on the object at all times, and detecting renames, unlinks
+etc. is difficult.
+.PP
+\fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR
+.IX Subsection "stat () is a synchronous operation"
+.PP
+Libev doesn't normally do any kind of I/O itself, and so is not blocking
+the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat
+()\*(C'\fR, which is a synchronous operation.
+.PP
+For local paths, this usually doesn't matter: unless the system is very
+busy or the intervals between stat's are large, a stat call will be fast,
+as the path data is usually in memory already (except when starting the
+watcher).
+.PP
+For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite
+time due to network issues, and even under good conditions, a stat call
+often takes multiple milliseconds.
+.PP
+Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked
+paths, although this is fully supported by libev.
 .PP
 \fIThe special problem of stat time resolution\fR
 .IX Subsection "The special problem of stat time resolution"
 .PP
-The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, and
+The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably,
-even on systems where the resolution is higher, many file systems still
+and even on systems where the resolution is higher, most file systems
-only support whole seconds.
+still only support whole seconds.
 .PP
 That means that, if the time is the only thing that changes, you can
 easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and
 calls your callback, which does something. When there is another update
-within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect it as the stat
+within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the
-data does not change.
+stat data does change in other ways (e.g. file size).
 .PP
 The solution to this is to delay acting on a change for slightly more
 than a second (or till slightly after the next full second boundary), using
 a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02);
 ev_timer_again (loop, w)\*(C'\fR).
 \&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
 be detected and should normally be specified as \f(CW0\fR to let libev choose
 a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
 path for as long as the watcher is active.
 .Sp
-The callback will receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected, relative
+The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event when a change was detected,
-to the attributes at the time the watcher was started (or the last change
+relative to the attributes at the time the watcher was started (or the
-was detected).
+last change was detected).
 .IP "ev_stat_stat (loop, ev_stat *)" 4
 .IX Item "ev_stat_stat (loop, ev_stat *)"
 Updates the stat buffer immediately with new values. If you change the
 watched path in your callback, you could call this function to avoid
 detecting this change (while introducing a race condition if you are not
 \&   ...
 \&   ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
 \&   ev_stat_start (loop, &passwd);
 \&   ev_timer_init (&timer, timer_cb, 0., 1.02);
 .Ve
-.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
+.ie n .SS """ev_idle"" \- when you've got nothing better to do..."
-.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
+.el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..."
 .IX Subsection "ev_idle - when you've got nothing better to do..."
 Idle watchers trigger events when no other events of the same or higher
-priority are pending (prepare, check and other idle watchers do not
+priority are pending (prepare, check and other idle watchers do not count
-count).
+as receiving \*(L"events\*(R").
 .PP
 That is, as long as your process is busy handling sockets or timeouts
 (or even signals, imagine) of the same or higher priority it will not be
 triggered. But when your process is idle (or only lower-priority watchers
 are pending), the idle watchers are being called once per event loop
 \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the
 event loop has handled all outstanding events.
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
-.IP "ev_idle_init (ev_signal *, callback)" 4
+.IP "ev_idle_init (ev_idle *, callback)" 4
-.IX Item "ev_idle_init (ev_signal *, callback)"
+.IX Item "ev_idle_init (ev_idle *, callback)"
 Initialises and configures the idle watcher \- it has no parameters of any
 kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
 believe me.
 .PP
 \fIExamples\fR
 Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
 callback, free it. Also, use no error checking, as usual.
 .PP
 .Vb 7
 \&   static void
-\&   idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
+\&   idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
 \&   {
 \&     free (w);
 \&     // now do something you wanted to do when the program has
 \&     // no longer anything immediate to do.
 \&   }
 \&
-\&   struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
+\&   ev_idle *idle_watcher = malloc (sizeof (ev_idle));
 \&   ev_idle_init (idle_watcher, idle_cb);
-\&   ev_idle_start (loop, idle_cb);
+\&   ev_idle_start (loop, idle_watcher);
 .Ve
-.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
+.ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!"
-.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
+.el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
 .IX Subsection "ev_prepare and ev_check - customise your event loop!"
-Prepare and check watchers are usually (but not always) used in tandem:
+Prepare and check watchers are usually (but not always) used in pairs:
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 .PP
 You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
 the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
 those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
 \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
 called in pairs bracketing the blocking call.
 .PP
 Their main purpose is to integrate other event mechanisms into libev and
-their use is somewhat advanced. This could be used, for example, to track
+their use is somewhat advanced. They could be used, for example, to track
 variable changes, implement your own watchers, integrate net-snmp or a
 coroutine library and lots more. They are also occasionally useful if
 you cache some data and want to flush it before blocking (for example,
 in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
 watcher).
 .PP
-This is done by examining in each prepare call which file descriptors need
+This is done by examining in each prepare call which file descriptors
-to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
+need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers
-them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
+for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many
-provide just this functionality). Then, in the check watcher you check for
+libraries provide exactly this functionality). Then, in the check watcher,
-any events that occurred (by checking the pending status of all watchers
+you check for any events that occurred (by checking the pending status
-and stopping them) and call back into the library. The I/O and timer
+of all watchers and stopping them) and call back into the library. The
-callbacks will never actually be called (but must be valid nevertheless,
+I/O and timer callbacks will never actually be called (but must be valid
-because you never know, you know?).
+nevertheless, because you never know, you know?).
 .PP
 As another example, the Perl Coro module uses these hooks to integrate
 coroutines into libev programs, by yielding to other active coroutines
 during each prepare and only letting the process block if no coroutines
 are ready to run (it's actually more complicated: it only runs coroutines
 loop from blocking if lower-priority coroutines are active, thus mapping
 low-priority coroutines to idle/background tasks).
 .PP
 It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
 priority, to ensure that they are being run before any other watchers
+after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR watchers).
+.PP
-after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
+Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not
-too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
+activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they
-supports this, they might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers
+might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As
-did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other
+\&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event
-(non-libev) event loops those other event loops might be in an unusable
+loops those other event loops might be in an unusable state until their
-state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to
+\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
-coexist peacefully with others).
+others).
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_prepare_init (ev_prepare *, callback)" 4
 .IX Item "ev_prepare_init (ev_prepare *, callback)"
 .IP "ev_check_init (ev_check *, callback)" 4
 .IX Item "ev_check_init (ev_check *, callback)"
 .PD
 Initialises and configures the prepare or check watcher \- they have no
 parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
-macros, but using them is utterly, utterly and completely pointless.
+macros, but using them is utterly, utterly, utterly and completely
+pointless.
 .PP
 \fIExamples\fR
 .IX Subsection "Examples"
 .PP
 There are a number of principal ways to embed other event loops or modules
 .Vb 2
 \&   static ev_io iow [nfd];
 \&   static ev_timer tw;
 \&
 \&   static void
-\&   io_cb (ev_loop *loop, ev_io *w, int revents)
+\&   io_cb (struct ev_loop *loop, ev_io *w, int revents)
 \&   {
 \&   }
 \&
 \&   // create io watchers for each fd and a timer before blocking
 \&   static void
-\&   adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
+\&   adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
 \&   {
 \&     int timeout = 3600000;
 \&     struct pollfd fds [nfd];
 \&     // actual code will need to loop here and realloc etc.
 \&     adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
 \&
 \&     /* the callback is illegal, but won\*(Aqt be called as we stop during check */
-\&     ev_timer_init (&tw, 0, timeout * 1e\-3);
+\&     ev_timer_init (&tw, 0, timeout * 1e\-3, 0.);
 \&     ev_timer_start (loop, &tw);
 \&
 \&     // create one ev_io per pollfd
 \&     for (int i = 0; i < nfd; ++i)
 \&       {
 \&       }
 \&   }
 \&
 \&   // stop all watchers after blocking
 \&   static void
-\&   adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+\&   adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
 \&   {
 \&     ev_timer_stop (loop, &tw);
 \&
 \&     for (int i = 0; i < nfd; ++i)
 \&       {
 \&
 \&   // do not ever call adns_afterpoll
 .Ve
 .PP
 Method 4: Do not use a prepare or check watcher because the module you
-want to embed is too inflexible to support it. Instead, you can override
+want to embed is not flexible enough to support it. Instead, you can
-their poll function.  The drawback with this solution is that the main
+override their poll function. The drawback with this solution is that the
-loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
+main loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module uses
-this.
+this approach, effectively embedding \s-1EV\s0 as a client into the horrible
+libglib event loop.
 .PP
 .Vb 4
 \&   static gint
 \&   event_poll_func (GPollFD *fds, guint nfds, gint timeout)
 \&   {
 \&       ev_io_stop (EV_A_ iow [n]);
 \&
 \&     return got_events;
 \&   }
 .Ve
-.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
+.ie n .SS """ev_embed"" \- when one backend isn't enough..."
-.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
+.el .SS "\f(CWev_embed\fP \- when one backend isn't enough..."
 .IX Subsection "ev_embed - when one backend isn't enough..."
 This is a rather advanced watcher type that lets you embed one event loop
 into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
 loop, other types of watchers might be handled in a delayed or incorrect
 fashion and must not be used).
 prioritise I/O.
 .PP
 As an example for a bug workaround, the kqueue backend might only support
 sockets on some platform, so it is unusable as generic backend, but you
 still want to make use of it because you have many sockets and it scales
-so nicely. In this case, you would create a kqueue-based loop and embed it
+so nicely. In this case, you would create a kqueue-based loop and embed
-into your default loop (which might use e.g. poll). Overall operation will
+it into your default loop (which might use e.g. poll). Overall operation
-be a bit slower because first libev has to poll and then call kevent, but
+will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then
-at least you can use both at what they are best.
+\&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are
+best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :)
 .PP
-As for prioritising I/O: rarely you have the case where some fds have
+As for prioritising I/O: under rare circumstances you have the case where
-to be watched and handled very quickly (with low latency), and even
+some fds have to be watched and handled very quickly (with low latency),
-priorities and idle watchers might have too much overhead. In this case
+and even priorities and idle watchers might have too much overhead. In
-you would put all the high priority stuff in one loop and all the rest in
+this case you would put all the high priority stuff in one loop and all
-a second one, and embed the second one in the first.
+the rest in a second one, and embed the second one in the first.
 .PP
-As long as the watcher is active, the callback will be invoked every time
+As long as the watcher is active, the callback will be invoked every
-there might be events pending in the embedded loop. The callback must then
+time there might be events pending in the embedded loop. The callback
-call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
+must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single
-their callbacks (you could also start an idle watcher to give the embedded
+sweep and invoke their callbacks (the callback doesn't need to invoke the
-loop strictly lower priority for example). You can also set the callback
+\&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher
-to \f(CW0\fR, in which case the embed watcher will automatically execute the
+to give the embedded loop strictly lower priority for example).
-embedded loop sweep.
 .PP
-As long as the watcher is started it will automatically handle events. The
+You can also set the callback to \f(CW0\fR, in which case the embed watcher
-callback will be invoked whenever some events have been handled. You can
+will automatically execute the embedded loop sweep whenever necessary.
-set the callback to \f(CW0\fR to avoid having to specify one if you are not
-interested in that.
 .PP
-Also, there have not currently been made special provisions for forking:
+Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher
-when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
+is active, i.e., the embedded loop will automatically be forked when the
-but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
+embedding loop forks. In other cases, the user is responsible for calling
-yourself.
+\&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop.
 .PP
-Unfortunately, not all backends are embeddable, only the ones returned by
+Unfortunately, not all backends are embeddable: only the ones returned by
 \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
 portable one.
 .PP
 So when you want to use this feature you will always have to be prepared
 that you cannot get an embeddable loop. The recommended way to get around
 this is to have a separate variables for your embeddable loop, try to
 create it, and if that fails, use the normal loop for everything.
+.PP
+\fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR
+.IX Subsection "ev_embed and fork"
+.PP
+While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will
+automatically be applied to the embedded loop as well, so no special
+fork handling is required in that case. When the watcher is not running,
+however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR
+as applicable.
 .PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
 .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
 used).
 .PP
 .Vb 3
 \&   struct ev_loop *loop_hi = ev_default_init (0);
 \&   struct ev_loop *loop_lo = 0;
-\&   struct ev_embed embed;
+\&   ev_embed embed;
 \&
 \&   // see if there is a chance of getting one that works
 \&   // (remember that a flags value of 0 means autodetection)
 \&   loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
 \&     ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
 \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too).
 .PP
 .Vb 3
 \&   struct ev_loop *loop = ev_default_init (0);
 \&   struct ev_loop *loop_socket = 0;
-\&   struct ev_embed embed;
+\&   ev_embed embed;
 \&
 \&   if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
 \&     if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
 \&       {
 \&         ev_embed_init (&embed, 0, loop_socket);
 \&   if (!loop_socket)
 \&     loop_socket = loop;
 \&
 \&   // now use loop_socket for all sockets, and loop for everything else
 .Ve
-.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
+.ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork"
-.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
+.el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
 .IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
 Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
 whoever is a good citizen cared to tell libev about it by calling
 \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
 event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
 and only in the child after the fork. If whoever good citizen calling
 \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
 handlers will be invoked, too, of course.
 .PP
+\fIThe special problem of life after fork \- how is it possible?\fR
+.IX Subsection "The special problem of life after fork - how is it possible?"
+.PP
+Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to ste
+up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This
+sequence should be handled by libev without any problems.
+.PP
+This changes when the application actually wants to do event handling
+in the child, or both parent in child, in effect \*(L"continuing\*(R" after the
+fork.
+.PP
+The default mode of operation (for libev, with application help to detect
+forks) is to duplicate all the state in the child, as would be expected
+when \fIeither\fR the parent \fIor\fR the child process continues.
+.PP
+When both processes want to continue using libev, then this is usually the
+wrong result. In that case, usually one process (typically the parent) is
+supposed to continue with all watchers in place as before, while the other
+process typically wants to start fresh, i.e. without any active watchers.
+.PP
+The cleanest and most efficient way to achieve that with libev is to
+simply create a new event loop, which of course will be \*(L"empty\*(R", and
+use that for new watchers. This has the advantage of not touching more
+memory than necessary, and thus avoiding the copy-on-write, and the
+disadvantage of having to use multiple event loops (which do not support
+signal watchers).
+.PP
+When this is not possible, or you want to use the default loop for
+other reasons, then in the process that wants to start \*(L"fresh\*(R", call
+\&\f(CW\*(C`ev_default_destroy ()\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR. Destroying
+the default loop will \*(L"orphan\*(R" (not stop) all registered watchers, so you
+have to be careful not to execute code that modifies those watchers. Note
+also that in that case, you have to re-register any signal watchers.
+.PP
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_fork_init (ev_signal *, callback)" 4
 .IX Item "ev_fork_init (ev_signal *, callback)"
 Initialises and configures the fork watcher \- it has no parameters of any
 kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
 believe me.
-.ie n .Sh """ev_async"" \- how to wake up another event loop"
+.ie n .SS """ev_async"" \- how to wake up another event loop"
-.el .Sh "\f(CWev_async\fP \- how to wake up another event loop"
+.el .SS "\f(CWev_async\fP \- how to wake up another event loop"
 .IX Subsection "ev_async - how to wake up another event loop"
 In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other
 asynchronous sources such as signal handlers (as opposed to multiple event
 loops \- those are of course safe to use in different threads).
 .PP
 is that the author does not know of a simple (or any) algorithm for a
 multiple-writer-single-reader queue that works in all cases and doesn't
 need elaborate support such as pthreads.
 .PP
 That means that if you want to queue data, you have to provide your own
-queue. But at least I can tell you would implement locking around your
+queue. But at least I can tell you how to implement locking around your
 queue:
 .IP "queueing from a signal handler context" 4
 .IX Item "queueing from a signal handler context"
 To implement race-free queueing, you simply add to the queue in the signal
-handler but you block the signal handler in the watcher callback. Here is an example that does that for
+handler but you block the signal handler in the watcher callback. Here is
-some fictitious \s-1SIGUSR1\s0 handler:
+an example that does that for some fictitious \s-1SIGUSR1\s0 handler:
 .Sp
 .Vb 1
 \&   static ev_async mysig;
 \&
 \&   static void
 \fIWatcher-Specific Functions and Data Members\fR
 .IX Subsection "Watcher-Specific Functions and Data Members"
 .IP "ev_async_init (ev_async *, callback)" 4
 .IX Item "ev_async_init (ev_async *, callback)"
 Initialises and configures the async watcher \- it has no parameters of any
-kind. There is a \f(CW\*(C`ev_asynd_set\*(C'\fR macro, but using it is utterly pointless,
+kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless,
-believe me.
+trust me.
 .IP "ev_async_send (loop, ev_async *)" 4
 .IX Item "ev_async_send (loop, ev_async *)"
 Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds
 an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike
-\&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do in other threads, signal or
+\&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or
 similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding
 section below on what exactly this means).
 .Sp
+Note that, as with other watchers in libev, multiple events might get
+compressed into a single callback invocation (another way to look at this
+is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered, set on \f(CW\*(C`ev_async_send\*(C'\fR,
+reset when the event loop detects that).
+.Sp
-This call incurs the overhead of a system call only once per loop iteration,
+This call incurs the overhead of a system call only once per event loop
-so while the overhead might be noticeable, it doesn't apply to repeated
+iteration, so while the overhead might be noticeable, it doesn't apply to
-calls to \f(CW\*(C`ev_async_send\*(C'\fR.
+repeated calls to \f(CW\*(C`ev_async_send\*(C'\fR for the same event loop.
 .IP "bool = ev_async_pending (ev_async *)" 4
 .IX Item "bool = ev_async_pending (ev_async *)"
 Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the
 watcher but the event has not yet been processed (or even noted) by the
 event loop.
 \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When
 the loop iterates next and checks for the watcher to have become active,
 it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very
 quickly check whether invoking the loop might be a good idea.
 .Sp
-Not that this does \fInot\fR check whether the watcher itself is pending, only
+Not that this does \fInot\fR check whether the watcher itself is pending,
-whether it has been requested to make this watcher pending.
+only whether it has been requested to make this watcher pending: there
+is a time window between the event loop checking and resetting the async
+notification, and the callback being invoked.
 .SH "OTHER FUNCTIONS"
 .IX Header "OTHER FUNCTIONS"
 There are some other functions of possible interest. Described. Here. Now.
 .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
 .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
 This function combines a simple timer and an I/O watcher, calls your
-callback on whichever event happens first and automatically stop both
+callback on whichever event happens first and automatically stops both
 watchers. This is useful if you want to wait for a single event on an fd
 or timeout without having to allocate/configure/start/stop/free one or
 more watchers yourself.
 .Sp
-If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events
+If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the
-is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and
+\&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for
-\&\f(CW\*(C`events\*(C'\fR set will be created and started.
+the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started.
 .Sp
 If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be
 started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and
-repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of
+repeat = 0) will be started. \f(CW0\fR is a valid timeout.
-dubious value.
 .Sp
 The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets
 passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
 \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR
-value passed to \f(CW\*(C`ev_once\*(C'\fR:
+value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR
+a timeout and an io event at the same time \- you probably should give io
+events precedence.
+.Sp
+Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO\s0.
 .Sp
 .Vb 7
 \&   static void stdin_ready (int revents, void *arg)
 \&   {
+\&     if (revents & EV_READ)
+\&       /* stdin might have data for us, joy! */;
-\&     if (revents & EV_TIMEOUT)
+\&     else if (revents & EV_TIMEOUT)
 \&       /* doh, nothing entered */;
-\&     else if (revents & EV_READ)
-\&       /* stdin might have data for us, joy! */;
 \&   }
 \&
 \&   ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
 .Ve
-.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
+.IP "ev_feed_event (struct ev_loop *, watcher *, int revents)" 4
-.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
+.IX Item "ev_feed_event (struct ev_loop *, watcher *, int revents)"
 Feeds the given event set into the event loop, as if the specified event
 had happened for the specified watcher (which must be a pointer to an
 initialised but not necessarily started event watcher).
-.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
+.IP "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" 4
-.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
+.IX Item "ev_feed_fd_event (struct ev_loop *, int fd, int revents)"
 Feed an event on the given fd, as if a file descriptor backend detected
 the given events it.
-.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
+.IP "ev_feed_signal_event (struct ev_loop *loop, int signum)" 4
-.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
+.IX Item "ev_feed_signal_event (struct ev_loop *loop, int signum)"
 Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default
 loop!).
 .SH "LIBEVENT EMULATION"
 .IX Header "LIBEVENT EMULATION"
 Libev offers a compatibility emulation layer for libevent. It cannot
 need one additional pointer for context. If you need support for other
 types of functors please contact the author (preferably after implementing
 it).
 .PP
 Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
-.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
+.ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4
 .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
 .IX Item "ev::READ, ev::WRITE etc."
 These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
 macros from \fIev.h\fR.
-.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
+.ie n .IP """ev::tstamp"", ""ev::now""" 4
 .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
 .IX Item "ev::tstamp, ev::now"
 Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
-.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4
+.ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4
 .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
 .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
 For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
 the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
 which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
 \&
 \&   myclass obj;
 \&   ev::io iow;
 \&   iow.set <myclass, &myclass::io_cb> (&obj);
 .Ve
+.IP "w\->set (object *)" 4
+.IX Item "w->set (object *)"
+This is an \fBexperimental\fR feature that might go away in a future version.
+.Sp
+This is a variation of a method callback \- leaving out the method to call
+will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use
+functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all
+the time. Incidentally, you can then also leave out the template argument
+list.
+.Sp
+The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w,
+int revents)\*(C'\fR.
+.Sp
+See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
+.Sp
+Example: use a functor object as callback.
+.Sp
+.Vb 7
+\&   struct myfunctor
+\&   {
+\&     void operator() (ev::io &w, int revents)
+\&     {
+\&       ...
+\&     }
+\&   }
+\&
+\&   myfunctor f;
+\&
+\&   ev::io w;
+\&   w.set (&f);
+.Ve
 .IP "w\->set<function> (void *data = 0)" 4
 .IX Item "w->set<function> (void *data = 0)"
 Also sets a callback, but uses a static method or plain function as
 callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
 \&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
 .Sp
 The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
 .Sp
 See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
 .Sp
-Example:
+Example: Use a plain function as callback.
 .Sp
 .Vb 2
 \&   static void io_cb (ev::io &w, int revents) { }
 \&   iow.set <io_cb> ();
 .Ve
 Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
 constructor already stores the event loop.
 .IP "w\->stop ()" 4
 .IX Item "w->stop ()"
 Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
-.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
+.ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4
 .el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
 .IX Item "w->again () (ev::timer, ev::periodic only)"
 For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
 \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
 .ie n .IP "w\->sweep () (""ev::embed"" only)" 4
 the constructor.
 .PP
 .Vb 4
 \&   class myclass
 \&   {
-\&     ev::io   io;  void io_cb   (ev::io   &w, int revents);
+\&     ev::io   io  ; void io_cb   (ev::io   &w, int revents);
-\&     ev:idle idle  void idle_cb (ev::idle &w, int revents);
+\&     ev::idle idle; void idle_cb (ev::idle &w, int revents);
 \&
 \&     myclass (int fd)
 \&     {
 \&       io  .set <myclass, &myclass::io_cb  > (this);
 \&       idle.set <myclass, &myclass::idle_cb> (this);
 .IP "Perl" 4
 .IX Item "Perl"
 The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test
 libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module,
 there are additional modules that implement libev-compatible interfaces
-to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR), \f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the
+to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays),
-\&\f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR and \f(CW\*(C`EV::Glib\*(C'\fR).
+\&\f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the \f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR
+and \f(CW\*(C`EV::Glib\*(C'\fR).
 .Sp
 It can be found and installed via \s-1CPAN\s0, its homepage is at
 <http://software.schmorp.de/pkg/EV>.
 .IP "Python" 4
 .IX Item "Python"
 Python bindings can be found at <http://code.google.com/p/pyev/>. It
-seems to be quite complete and well-documented. Note, however, that the
+seems to be quite complete and well-documented.
-patch they require for libev is outright dangerous as it breaks the \s-1ABI\s0
-for everybody else, and therefore, should never be applied in an installed
-libev (if python requires an incompatible \s-1ABI\s0 then it needs to embed
-libev).
 .IP "Ruby" 4
 .IX Item "Ruby"
 Tony Arcieri has written a ruby extension that offers access to a subset
 of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and
 more on top of it. It can be found via gem servers. Its homepage is at
 <http://rev.rubyforge.org/>.
+.Sp
+Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR
+makes rev work even on mingw.
+.IP "Haskell" 4
+.IX Item "Haskell"
+A haskell binding to libev is available at
+<http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>.
 .IP "D" 4
 .IX Item "D"
 Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to
-be found at <http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
+be found at <http://proj.llucax.com.ar/wiki/evd>.
+.IP "Ocaml" 4
+.IX Item "Ocaml"
+Erkki Seppala has written Ocaml bindings for libev, to be found at
+<http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>.
 .SH "MACRO MAGIC"
 .IX Header "MACRO MAGIC"
 Libev can be compiled with a variety of options, the most fundamental
 of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
 functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
 .PP
 To make it easier to write programs that cope with either variant, the
 following macros are defined:
-.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
+.ie n .IP """EV_A"", ""EV_A_""" 4
 .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
 .IX Item "EV_A, EV_A_"
 This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
 loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
 \&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
 \&   ev_loop (EV_A_ 0);
 .Ve
 .Sp
 It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
 which is often provided by the following macro.
-.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
+.ie n .IP """EV_P"", ""EV_P_""" 4
 .el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
 .IX Item "EV_P, EV_P_"
 This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
 loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
 \&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
 \&   static void cb (EV_P_ ev_timer *w, int revents)
 .Ve
 .Sp
 It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
 suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
-.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
+.ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4
 .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
 .IX Item "EV_DEFAULT, EV_DEFAULT_"
 Similar to the other two macros, this gives you the value of the default
 loop, if multiple loops are supported (\*(L"ev loop default\*(R").
-.ie n .IP """EV_DEFAULT_UC""\fR, \f(CW""EV_DEFAULT_UC_""" 4
+.ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4
 .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4
 .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_"
 Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the
 default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour
 is undefined when the default loop has not been initialised by a previous
 .PP
 The goal is to enable you to just copy the necessary files into your
 source directory without having to change even a single line in them, so
 you can easily upgrade by simply copying (or having a checked-out copy of
 libev somewhere in your source tree).
-.Sh "\s-1FILESETS\s0"
+.SS "\s-1FILESETS\s0"
 .IX Subsection "FILESETS"
 Depending on what features you need you need to include one or more sets of files
 in your application.
 .PP
 \fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
 \&   #define EV_STANDALONE 1
 \&   #include "ev.h"
 .Ve
 .PP
 Both header files and implementation files can be compiled with a \*(C+
-compiler (at least, thats a stated goal, and breakage will be treated
+compiler (at least, that's a stated goal, and breakage will be treated
 as a bug).
 .PP
 You need the following files in your source tree, or in a directory
 in your include path (e.g. in libev/ when using \-Ilibev):
 .PP
 For this of course you need the m4 file:
 .PP
 .Vb 1
 \&   libev.m4
 .Ve
-.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
+.SS "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
 .IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
 Libev can be configured via a variety of preprocessor symbols you have to
 define before including any of its files. The default in the absence of
-autoconf is noted for every option.
+autoconf is documented for every option.
 .IP "\s-1EV_STANDALONE\s0" 4
 .IX Item "EV_STANDALONE"
 Must always be \f(CW1\fR if you do not use autoconf configuration, which
 keeps libev from including \fIconfig.h\fR, and it also defines dummy
 implementations for some libevent functions (such as logging, which is not
 supported). It will also not define any of the structs usually found in
 \&\fIevent.h\fR that are not directly supported by the libev core alone.
+.Sp
+In stanbdalone mode, libev will still try to automatically deduce the
+configuration, but has to be more conservative.
 .IP "\s-1EV_USE_MONOTONIC\s0" 4
 .IX Item "EV_USE_MONOTONIC"
 If defined to be \f(CW1\fR, libev will try to detect the availability of the
-monotonic clock option at both compile time and runtime. Otherwise no use
+monotonic clock option at both compile time and runtime. Otherwise no
-of the monotonic clock option will be attempted. If you enable this, you
+use of the monotonic clock option will be attempted. If you enable this,
-usually have to link against librt or something similar. Enabling it when
+you usually have to link against librt or something similar. Enabling it
-the functionality isn't available is safe, though, although you have
+when the functionality isn't available is safe, though, although you have
 to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
-function is hiding in (often \fI\-lrt\fR).
+function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
 .IP "\s-1EV_USE_REALTIME\s0" 4
 .IX Item "EV_USE_REALTIME"
 If defined to be \f(CW1\fR, libev will try to detect the availability of the
-real-time clock option at compile time (and assume its availability at
+real-time clock option at compile time (and assume its availability
-runtime if successful). Otherwise no use of the real-time clock option will
+at runtime if successful). Otherwise no use of the real-time clock
-be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
+option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR
-(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
+by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect
-note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
+correctness. See the note about libraries in the description of
+\&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of
+\&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR.
+.IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4
+.IX Item "EV_USE_CLOCK_SYSCALL"
+If defined to be \f(CW1\fR, libev will try to use a direct syscall instead
+of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option
+exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR
+unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded
+programs needlessly. Using a direct syscall is slightly slower (in
+theory), because no optimised vdso implementation can be used, but avoids
+the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or
+higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
 .IP "\s-1EV_USE_NANOSLEEP\s0" 4
 .IX Item "EV_USE_NANOSLEEP"
 If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
 and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
 .IP "\s-1EV_USE_EVENTFD\s0" 4
 will not be compiled in.
 .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
 .IX Item "EV_SELECT_USE_FD_SET"
 If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
 structure. This is useful if libev doesn't compile due to a missing
-\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout on
+\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout
-exotic systems. This usually limits the range of file descriptors to some
+on exotic systems. This usually limits the range of file descriptors to
-low limit such as 1024 or might have other limitations (winsocket only
+some low limit such as 1024 or might have other limitations (winsocket
-allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
+only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation,
-influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
+configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR.
 .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
 .IX Item "EV_SELECT_IS_WINSOCKET"
 When defined to \f(CW1\fR, the select backend will assume that
 select/socket/connect etc. don't understand file descriptors but
 wants osf handles on win32 (this is the case when the select to
 When doing priority-based operations, libev usually has to linearly search
 all the priorities, so having many of them (hundreds) uses a lot of space
 and time, so using the defaults of five priorities (\-2 .. +2) is usually
 fine.
 .Sp
-If your embedding application does not need any priorities, defining these both to
+If your embedding application does not need any priorities, defining these
-\&\f(CW0\fR will save some memory and \s-1CPU\s0.
+both to \f(CW0\fR will save some memory and \s-1CPU\s0.
 .IP "\s-1EV_PERIODIC_ENABLE\s0" 4
 .IX Item "EV_PERIODIC_ENABLE"
 If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
 defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
 code.
 defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
 code.
 .IP "\s-1EV_EMBED_ENABLE\s0" 4
 .IX Item "EV_EMBED_ENABLE"
 If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
-defined to be \f(CW0\fR, then they are not.
+defined to be \f(CW0\fR, then they are not. Embed watchers rely on most other
+watcher types, which therefore must not be disabled.
 .IP "\s-1EV_STAT_ENABLE\s0" 4
 .IX Item "EV_STAT_ENABLE"
 If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
 defined to be \f(CW0\fR, then they are not.
 .IP "\s-1EV_FORK_ENABLE\s0" 4
 If undefined or defined to be \f(CW1\fR, then async watchers are supported. If
 defined to be \f(CW0\fR, then they are not.
 .IP "\s-1EV_MINIMAL\s0" 4
 .IX Item "EV_MINIMAL"
 If you need to shave off some kilobytes of code at the expense of some
-speed, define this symbol to \f(CW1\fR. Currently this is used to override some
+speed (but with the full \s-1API\s0), define this symbol to \f(CW1\fR. Currently this
-inlining decisions, saves roughly 30% code size on amd64. It also selects a
+is used to override some inlining decisions, saves roughly 30% code size
-much smaller 2\-heap for timer management over the default 4\-heap.
+on amd64. It also selects a much smaller 2\-heap for timer management over
+the default 4\-heap.
+.Sp
+You can save even more by disabling watcher types you do not need
+and setting \f(CW\*(C`EV_MAXPRI\*(C'\fR == \f(CW\*(C`EV_MINPRI\*(C'\fR. Also, disabling \f(CW\*(C`assert\*(C'\fR
+(\f(CW\*(C`\-DNDEBUG\*(C'\fR) will usually reduce code size a lot.
+.Sp
+Defining \f(CW\*(C`EV_MINIMAL\*(C'\fR to \f(CW2\fR will additionally reduce the core \s-1API\s0 to
+provide a bare-bones event library. See \f(CW\*(C`ev.h\*(C'\fR for details on what parts
+of the \s-1API\s0 are still available, and do not complain if this subset changes
+over time.
 .IP "\s-1EV_PID_HASHSIZE\s0" 4
 .IX Item "EV_PID_HASHSIZE"
 \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
 pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
 than enough. If you need to manage thousands of children you might want to
 watchers you might want to increase this value (\fImust\fR be a power of
 two).
 .IP "\s-1EV_USE_4HEAP\s0" 4
 .IX Item "EV_USE_4HEAP"
 Heaps are not very cache-efficient. To improve the cache-efficiency of the
-timer and periodics heap, libev uses a 4\-heap when this symbol is defined
+timer and periodics heaps, libev uses a 4\-heap when this symbol is defined
-to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has
+to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably
-noticeably faster performance with many (thousands) of watchers.
+faster performance with many (thousands) of watchers.
 .Sp
 The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR
 (disabled).
 .IP "\s-1EV_HEAP_CACHE_AT\s0" 4
 .IX Item "EV_HEAP_CACHE_AT"
 Heaps are not very cache-efficient. To improve the cache-efficiency of the
-timer and periodics heap, libev can cache the timestamp (\fIat\fR) within
+timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within
 the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR),
 which uses 8\-12 bytes more per watcher and a few hundred bytes more code,
 but avoids random read accesses on heap changes. This improves performance
-noticeably with with many (hundreds) of watchers.
+noticeably with many (hundreds) of watchers.
 .Sp
 The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR
 (disabled).
 .IP "\s-1EV_VERIFY\s0" 4
 .IX Item "EV_VERIFY"
 called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
 verification code will be called very frequently, which will slow down
 libev considerably.
 .Sp
 The default is \f(CW1\fR, unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set, in which case it will be
-\&\f(CW0.\fR
+\&\f(CW0\fR.
 .IP "\s-1EV_COMMON\s0" 4
 .IX Item "EV_COMMON"
 By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
 this macro to a something else you can include more and other types of
 members. You have to define it each time you include one of the files,
 and the way callbacks are invoked and set. Must expand to a struct member
 definition and a statement, respectively. See the \fIev.h\fR header file for
 their default definitions. One possible use for overriding these is to
 avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
 method calls instead of plain function calls in \*(C+.
-.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
+.SS "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
 .IX Subsection "EXPORTED API SYMBOLS"
 If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of
 exported symbols, you can use the provided \fISymbol.*\fR files which list
 all public symbols, one per line:
 .PP
 \&   #define ev_backend     myprefix_ev_backend
 \&   #define ev_check_start myprefix_ev_check_start
 \&   #define ev_check_stop  myprefix_ev_check_stop
 \&   ...
 .Ve
-.Sh "\s-1EXAMPLES\s0"
+.SS "\s-1EXAMPLES\s0"
 .IX Subsection "EXAMPLES"
 For a real-world example of a program the includes libev
 verbatim, you can have a look at the \s-1EV\s0 perl module
 (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
 the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
 .PP
 .Vb 2
 \&   #include "ev_cpp.h"
 \&   #include "ev.c"
 .Ve
-.SH "THREADS AND COROUTINES"
+.SH "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES"
+.IX Header "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES"
+.SS "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0"
-.IX Header "THREADS AND COROUTINES"
+.IX Subsection "THREADS AND COROUTINES"
-.Sh "\s-1THREADS\s0"
+\fI\s-1THREADS\s0\fR
 .IX Subsection "THREADS"
-Libev itself is completely thread-safe, but it uses no locking. This
+.PP
+All libev functions are reentrant and thread-safe unless explicitly
+documented otherwise, but libev implements no locking itself. This means
-means that you can use as many loops as you want in parallel, as long as
+that you can use as many loops as you want in parallel, as long as there
-only one thread ever calls into one libev function with the same loop
+are no concurrent calls into any libev function with the same loop
-parameter.
+parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter,
+of course): libev guarantees that different event loops share no data
+structures that need any locking.
 .PP
-Or put differently: calls with different loop parameters can be done in
+Or to put it differently: calls with different loop parameters can be done
-parallel from multiple threads, calls with the same loop parameter must be
+concurrently from multiple threads, calls with the same loop parameter
-done serially (but can be done from different threads, as long as only one
+must be done serially (but can be done from different threads, as long as
-thread ever is inside a call at any point in time, e.g. by using a mutex
+only one thread ever is inside a call at any point in time, e.g. by using
-per loop).
+a mutex per loop).
 .PP
-If you want to know which design is best for your problem, then I cannot
+Specifically to support threads (and signal handlers), libev implements
+so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of
+concurrency on the same event loop, namely waking it up \*(L"from the
+outside\*(R".
+.PP
+If you want to know which design (one loop, locking, or multiple loops
+without or something else still) is best for your problem, then I cannot
-help you but by giving some generic advice:
+help you, but here is some generic advice:
 .IP "\(bu" 4
 most applications have a main thread: use the default libev loop
 in that thread, or create a separate thread running only the default loop.
 .Sp
 This helps integrating other libraries or software modules that use libev
 .Sp
 Choosing a model is hard \- look around, learn, know that usually you can do
 better than you currently do :\-)
 .IP "\(bu" 4
 often you need to talk to some other thread which blocks in the
+event loop.
+.Sp
-event loop \- \f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other
+\&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely
-threads safely (or from signal contexts...).
+(or from signal contexts...).
-.Sh "\s-1COROUTINES\s0"
+.Sp
+An example use would be to communicate signals or other events that only
+work in the default loop by registering the signal watcher with the
+default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop
+watcher callback into the event loop interested in the signal.
+.PP
+\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0
+.IX Subsection "THREAD LOCKING EXAMPLE"
+.PP
+Here is a fictitious example of how to run an event loop in a different
+thread than where callbacks are being invoked and watchers are
+created/added/removed.
+.PP
+For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module,
+which uses exactly this technique (which is suited for many high-level
+languages).
+.PP
+The example uses a pthread mutex to protect the loop data, a condition
+variable to wait for callback invocations, an async watcher to notify the
+event loop thread and an unspecified mechanism to wake up the main thread.
+.PP
+First, you need to associate some data with the event loop:
+.PP
+.Vb 6
+\&   typedef struct {
+\&     mutex_t lock; /* global loop lock */
+\&     ev_async async_w;
+\&     thread_t tid;
+\&     cond_t invoke_cv;
+\&   } userdata;
+\&
+\&   void prepare_loop (EV_P)
+\&   {
+\&      // for simplicity, we use a static userdata struct.
+\&      static userdata u;
+\&
+\&      ev_async_init (&u\->async_w, async_cb);
+\&      ev_async_start (EV_A_ &u\->async_w);
+\&
+\&      pthread_mutex_init (&u\->lock, 0);
+\&      pthread_cond_init (&u\->invoke_cv, 0);
+\&
+\&      // now associate this with the loop
+\&      ev_set_userdata (EV_A_ u);
+\&      ev_set_invoke_pending_cb (EV_A_ l_invoke);
+\&      ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
+\&
+\&      // then create the thread running ev_loop
+\&      pthread_create (&u\->tid, 0, l_run, EV_A);
+\&   }
+.Ve
+.PP
+The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
+solely to wake up the event loop so it takes notice of any new watchers
+that might have been added:
+.PP
+.Vb 5
+\&   static void
+\&   async_cb (EV_P_ ev_async *w, int revents)
+\&   {
+\&      // just used for the side effects
+\&   }
+.Ve
+.PP
+The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex
+protecting the loop data, respectively.
+.PP
+.Vb 6
+\&   static void
+\&   l_release (EV_P)
+\&   {
+\&     userdata *u = ev_userdata (EV_A);
+\&     pthread_mutex_unlock (&u\->lock);
+\&   }
+\&
+\&   static void
+\&   l_acquire (EV_P)
+\&   {
+\&     userdata *u = ev_userdata (EV_A);
+\&     pthread_mutex_lock (&u\->lock);
+\&   }
+.Ve
+.PP
+The event loop thread first acquires the mutex, and then jumps straight
+into \f(CW\*(C`ev_loop\*(C'\fR:
+.PP
+.Vb 4
+\&   void *
+\&   l_run (void *thr_arg)
+\&   {
+\&     struct ev_loop *loop = (struct ev_loop *)thr_arg;
+\&
+\&     l_acquire (EV_A);
+\&     pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
+\&     ev_loop (EV_A_ 0);
+\&     l_release (EV_A);
+\&
+\&     return 0;
+\&   }
+.Ve
+.PP
+Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will
+signal the main thread via some unspecified mechanism (signals? pipe
+writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers
+have been called (in a while loop because a) spurious wakeups are possible
+and b) skipping inter-thread-communication when there are no pending
+watchers is very beneficial):
+.PP
+.Vb 4
+\&   static void
+\&   l_invoke (EV_P)
+\&   {
+\&     userdata *u = ev_userdata (EV_A);
+\&
+\&     while (ev_pending_count (EV_A))
+\&       {
+\&         wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
+\&         pthread_cond_wait (&u\->invoke_cv, &u\->lock);
+\&       }
+\&   }
+.Ve
+.PP
+Now, whenever the main thread gets told to invoke pending watchers, it
+will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop
+thread to continue:
+.PP
+.Vb 4
+\&   static void
+\&   real_invoke_pending (EV_P)
+\&   {
+\&     userdata *u = ev_userdata (EV_A);
+\&
+\&     pthread_mutex_lock (&u\->lock);
+\&     ev_invoke_pending (EV_A);
+\&     pthread_cond_signal (&u\->invoke_cv);
+\&     pthread_mutex_unlock (&u\->lock);
+\&   }
+.Ve
+.PP
+Whenever you want to start/stop a watcher or do other modifications to an
+event loop, you will now have to lock:
+.PP
+.Vb 2
+\&   ev_timer timeout_watcher;
+\&   userdata *u = ev_userdata (EV_A);
+\&
+\&   ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+\&
+\&   pthread_mutex_lock (&u\->lock);
+\&   ev_timer_start (EV_A_ &timeout_watcher);
+\&   ev_async_send (EV_A_ &u\->async_w);
+\&   pthread_mutex_unlock (&u\->lock);
+.Ve
+.PP
+Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise
+an event loop currently blocking in the kernel will have no knowledge
+about the newly added timer. By waking up the loop it will pick up any new
+watchers in the next event loop iteration.
+.PP
+\fI\s-1COROUTINES\s0\fR
 .IX Subsection "COROUTINES"
+.PP
-Libev is much more accommodating to coroutines (\*(L"cooperative threads\*(R"):
+Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"):
-libev fully supports nesting calls to it's functions from different
+libev fully supports nesting calls to its functions from different
 coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two
-different coroutines and switch freely between both coroutines running the
+different coroutines, and switch freely between both coroutines running
-loop, as long as you don't confuse yourself). The only exception is that
+the loop, as long as you don't confuse yourself). The only exception is
-you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks.
+that you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks.
 .PP
-Care has been invested into making sure that libev does not keep local
+Care has been taken to ensure that libev does not keep local state inside
-state inside \f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow coroutine
+\&\f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow for coroutine switches as
+they do not call any callbacks.
+.SS "\s-1COMPILER\s0 \s-1WARNINGS\s0"
+.IX Subsection "COMPILER WARNINGS"
+Depending on your compiler and compiler settings, you might get no or a
+lot of warnings when compiling libev code. Some people are apparently
+scared by this.
+.PP
+However, these are unavoidable for many reasons. For one, each compiler
+has different warnings, and each user has different tastes regarding
+warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when
+targeting a specific compiler and compiler-version.
+.PP
+Another reason is that some compiler warnings require elaborate
+workarounds, or other changes to the code that make it less clear and less
+maintainable.
+.PP
+And of course, some compiler warnings are just plain stupid, or simply
+wrong (because they don't actually warn about the condition their message
+seems to warn about). For example, certain older gcc versions had some
+warnings that resulted an extreme number of false positives. These have
+been fixed, but some people still insist on making code warn-free with
+such buggy versions.
+.PP
+While libev is written to generate as few warnings as possible,
+\&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev
+with any compiler warnings enabled unless you are prepared to cope with
+them (e.g. by ignoring them). Remember that warnings are just that:
+warnings, not errors, or proof of bugs.
+.SS "\s-1VALGRIND\s0"
+.IX Subsection "VALGRIND"
+Valgrind has a special section here because it is a popular tool that is
+highly useful. Unfortunately, valgrind reports are very hard to interpret.
+.PP
+If you think you found a bug (memory leak, uninitialised data access etc.)
+in libev, then check twice: If valgrind reports something like:
+.PP
+.Vb 3
+\&   ==2274==    definitely lost: 0 bytes in 0 blocks.
+\&   ==2274==      possibly lost: 0 bytes in 0 blocks.
+\&   ==2274==    still reachable: 256 bytes in 1 blocks.
+.Ve
+.PP
+Then there is no memory leak, just as memory accounted to global variables
+is not a memleak \- the memory is still being referenced, and didn't leak.
+.PP
+Similarly, under some circumstances, valgrind might report kernel bugs
+as if it were a bug in libev (e.g. in realloc or in the poll backend,
+although an acceptable workaround has been found here), or it might be
+confused.
+.PP
+Keep in mind that valgrind is a very good tool, but only a tool. Don't
+make it into some kind of religion.
+.PP
+If you are unsure about something, feel free to contact the mailing list
+with the full valgrind report and an explanation on why you think this
+is a bug in libev (best check the archives, too :). However, don't be
+annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance
+of learning how to interpret valgrind properly.
+.PP
+If you need, for some reason, empty reports from valgrind for your project
+I suggest using suppression lists.
+.SH "PORTABILITY NOTES"
+.IX Header "PORTABILITY NOTES"
+.SS "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0"
+.IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
+Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
+requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
+model. Libev still offers limited functionality on this platform in
+the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
+descriptors. This only applies when using Win32 natively, not when using
+e.g. cygwin.
+.PP
+Lifting these limitations would basically require the full
+re-implementation of the I/O system. If you are into these kinds of
+things, then note that glib does exactly that for you in a very portable
+way (note also that glib is the slowest event library known to man).
+.PP
+There is no supported compilation method available on windows except
+embedding it into other applications.
+.PP
+Sensible signal handling is officially unsupported by Microsoft \- libev
+tries its best, but under most conditions, signals will simply not work.
+.PP
+Not a libev limitation but worth mentioning: windows apparently doesn't
+accept large writes: instead of resulting in a partial write, windows will
+either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large,
+so make sure you only write small amounts into your sockets (less than a
+megabyte seems safe, but this apparently depends on the amount of memory
+available).
+.PP
+Due to the many, low, and arbitrary limits on the win32 platform and
+the abysmal performance of winsockets, using a large number of sockets
+is not recommended (and not reasonable). If your program needs to use
+more than a hundred or so sockets, then likely it needs to use a totally
+different implementation for windows, as libev offers the \s-1POSIX\s0 readiness
+notification model, which cannot be implemented efficiently on windows
+(due to Microsoft monopoly games).
+.PP
+A typical way to use libev under windows is to embed it (see the embedding
+section for details) and use the following \fIevwrap.h\fR header file instead
+of \fIev.h\fR:
+.PP
+.Vb 2
+\&   #define EV_STANDALONE              /* keeps ev from requiring config.h */
+\&   #define EV_SELECT_IS_WINSOCKET 1   /* configure libev for windows select */
+\&
+\&   #include "ev.h"
+.Ve
+.PP
+And compile the following \fIevwrap.c\fR file into your project (make sure
+you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!):
+.PP
+.Vb 2
+\&   #include "evwrap.h"
+\&   #include "ev.c"
+.Ve
+.IP "The winsocket select function" 4
+.IX Item "The winsocket select function"
+The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it
+requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is
+also extremely buggy). This makes select very inefficient, and also
+requires a mapping from file descriptors to socket handles (the Microsoft
+C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the
+discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and
+\&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info.
+.Sp
+The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime
+libraries and raw winsocket select is:
+.Sp
+.Vb 2
+\&   #define EV_USE_SELECT 1
+\&   #define EV_SELECT_IS_WINSOCKET 1   /* forces EV_SELECT_USE_FD_SET, too */
+.Ve
+.Sp
+Note that winsockets handling of fd sets is O(n), so you can easily get a
+complexity in the O(nA\*^X) range when using win32.
+.IP "Limited number of file descriptors" 4
+.IX Item "Limited number of file descriptors"
+Windows has numerous arbitrary (and low) limits on things.
+.Sp
+Early versions of winsocket's select only supported waiting for a maximum
+of \f(CW64\fR handles (probably owning to the fact that all windows kernels
+can only wait for \f(CW64\fR things at the same time internally; Microsoft
+recommends spawning a chain of threads and wait for 63 handles and the
+previous thread in each. Sounds great!).
+.Sp
+Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
+to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
+call (which might be in libev or elsewhere, for example, perl and many
+other interpreters do their own select emulation on windows).
+.Sp
+Another limit is the number of file descriptors in the Microsoft runtime
+libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR
+fetish or something like this inside Microsoft). You can increase this
+by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR
+(another arbitrary limit), but is broken in many versions of the Microsoft
+runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets
+(depending on windows version and/or the phase of the moon). To get more,
+you need to wrap all I/O functions and provide your own fd management, but
+the cost of calling select (O(nA\*^X)) will likely make this unworkable.
+.SS "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\s0"
+.IX Subsection "PORTABILITY REQUIREMENTS"
+In addition to a working ISO-C implementation and of course the
+backend-specific APIs, libev relies on a few additional extensions:
+.ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4
+.el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4
+.IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *."
+Libev assumes not only that all watcher pointers have the same internal
+structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also
+assumes that the same (machine) code can be used to call any watcher
+callback: The watcher callbacks have different type signatures, but libev
+calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
+.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4
+.el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4
+.IX Item "sig_atomic_t volatile must be thread-atomic as well"
+The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as
+\&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different
+threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is
+believed to be sufficiently portable.
+.ie n .IP """sigprocmask"" must work in a threaded environment" 4
+.el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4
+.IX Item "sigprocmask must work in a threaded environment"
+Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not
+allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical
+pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main
+thread\*(R" or will block signals process-wide, both behaviours would
+be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and
+\&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however.
+.Sp
+The most portable way to handle signals is to block signals in all threads
+except the initial one, and run the default loop in the initial thread as
+well.
+.ie n .IP """long"" must be large enough for common memory allocation sizes" 4
+.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
+.IX Item "long must be large enough for common memory allocation sizes"
+To improve portability and simplify its \s-1API\s0, libev uses \f(CW\*(C`long\*(C'\fR internally
+instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX
+systems (Microsoft...) this might be unexpectedly low, but is still at
+least 31 bits everywhere, which is enough for hundreds of millions of
-switches.
+watchers.
+.ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4
+.el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4
+.IX Item "double must hold a time value in seconds with enough accuracy"
+The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to
+have at least 51 bits of mantissa (and 9 bits of exponent), which is good
+enough for at least into the year 4000. This requirement is fulfilled by
+implementations implementing \s-1IEEE\s0 754, which is basically all existing
+ones. With \s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least
+2200.
+.PP
+If you know of other additional requirements drop me a note.
-.SH "COMPLEXITIES"
+.SH "ALGORITHMIC COMPLEXITIES"
-.IX Header "COMPLEXITIES"
+.IX Header "ALGORITHMIC COMPLEXITIES"
 In this section the complexities of (many of) the algorithms used inside
-libev will be explained. For complexity discussions about backends see the
+libev will be documented. For complexity discussions about backends see
-documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
+the documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
 .PP
 All of the following are about amortised time: If an array needs to be
 extended, libev needs to realloc and move the whole array, but this
-happens asymptotically never with higher number of elements, so O(1) might
+happens asymptotically rarer with higher number of elements, so O(1) might
-mean it might do a lengthy realloc operation in rare cases, but on average
+mean that libev does a lengthy realloc operation in rare cases, but on
-it is much faster and asymptotically approaches constant time.
+average it is much faster and asymptotically approaches constant time.
 .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
 .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
 This means that, when you have a watcher that triggers in one hour and
-there are 100 watchers that would trigger before that then inserting will
+there are 100 watchers that would trigger before that, then inserting will
 have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers.
 .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4
 .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)"
-That means that changing a timer costs less than removing/adding them
+That means that changing a timer costs less than removing/adding them,
 as only the relative motion in the event queue has to be paid for.
 .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4
 .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)"
 These just add the watcher into an array or at the head of a list.
 .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4
 .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)"
 .PD 0
 .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
 .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
 .PD
-These watchers are stored in lists then need to be walked to find the
+These watchers are stored in lists, so they need to be walked to find the
 correct watcher to remove. The lists are usually short (you don't usually
-have many watchers waiting for the same fd or signal).
+have many watchers waiting for the same fd or signal: one is typical, two
+is rare).
 .IP "Finding the next timer in each loop iteration: O(1)" 4
 .IX Item "Finding the next timer in each loop iteration: O(1)"
 By virtue of using a binary or 4\-heap, the next timer is always found at a
 fixed position in the storage array.
 .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
 .IX Item "Priority handling: O(number_of_priorities)"
 .PD
 Priorities are implemented by allocating some space for each
 priority. When doing priority-based operations, libev usually has to
 linearly search all the priorities, but starting/stopping and activating
-watchers becomes O(1) w.r.t. priority handling.
+watchers becomes O(1) with respect to priority handling.
 .IP "Sending an ev_async: O(1)" 4
 .IX Item "Sending an ev_async: O(1)"
 .PD 0
 .IP "Processing ev_async_send: O(number_of_async_watchers)" 4
 .IX Item "Processing ev_async_send: O(number_of_async_watchers)"
 .IX Item "Processing signals: O(max_signal_number)"
 .PD
 Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR
 calls in the current loop iteration. Checking for async and signal events
 involves iterating over all running async watchers or all signal numbers.
-.SH "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
+.SH "GLOSSARY"
-.IX Header "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS"
+.IX Header "GLOSSARY"
-Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev
+.IP "active" 4
-requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0
+.IX Item "active"
-model. Libev still offers limited functionality on this platform in
+A watcher is active as long as it has been started (has been attached to
-the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket
+an event loop) but not yet stopped (disassociated from the event loop).
-descriptors. This only applies when using Win32 natively, not when using
+.IP "application" 4
-e.g. cygwin.
+.IX Item "application"
-.PP
+In this document, an application is whatever is using libev.
-Lifting these limitations would basically require the full
+.IP "callback" 4
-re-implementation of the I/O system. If you are into these kinds of
+.IX Item "callback"
-things, then note that glib does exactly that for you in a very portable
+The address of a function that is called when some event has been
-way (note also that glib is the slowest event library known to man).
+detected. Callbacks are being passed the event loop, the watcher that
-.PP
+received the event, and the actual event bitset.
-There is no supported compilation method available on windows except
+.IP "callback invocation" 4
-embedding it into other applications.
+.IX Item "callback invocation"
-.PP
+The act of calling the callback associated with a watcher.
-Not a libev limitation but worth mentioning: windows apparently doesn't
+.IP "event" 4
-accept large writes: instead of resulting in a partial write, windows will
+.IX Item "event"
-either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large,
+A change of state of some external event, such as data now being available
-so make sure you only write small amounts into your sockets (less than a
+for reading on a file descriptor, time having passed or simply not having
-megabyte seems safe, but thsi apparently depends on the amount of memory
+any other events happening anymore.
-available).
-.PP
-Due to the many, low, and arbitrary limits on the win32 platform and
-the abysmal performance of winsockets, using a large number of sockets
-is not recommended (and not reasonable). If your program needs to use
-more than a hundred or so sockets, then likely it needs to use a totally
-different implementation for windows, as libev offers the \s-1POSIX\s0 readiness
-notification model, which cannot be implemented efficiently on windows
-(Microsoft monopoly games).
-.PP
-A typical way to use libev under windows is to embed it (see the embedding
-section for details) and use the following \fIevwrap.h\fR header file instead
-of \fIev.h\fR:
-.PP
-.Vb 2
-\&   #define EV_STANDALONE              /* keeps ev from requiring config.h */
-\&   #define EV_SELECT_IS_WINSOCKET 1   /* configure libev for windows select */
-\&
-\&   #include "ev.h"
-.Ve
-.PP
-And compile the following \fIevwrap.c\fR file into your project (make sure
-you do \fInot\fR compile the \fIev.c\fR or any other embedded soruce files!):
-.PP
-.Vb 2
-\&   #include "evwrap.h"
-\&   #include "ev.c"
-.Ve
-.IP "The winsocket select function" 4
-.IX Item "The winsocket select function"
-The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it
-requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is
-also extremely buggy). This makes select very inefficient, and also
-requires a mapping from file descriptors to socket handles (the Microsoft
-C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the
-discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and
-\&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info.
 .Sp
-The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime
+In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or
-libraries and raw winsocket select is:
+\&\f(CW\*(C`EV_TIMEOUT\*(C'\fR).
+.IP "event library" 4
+.IX Item "event library"
+A software package implementing an event model and loop.
+.IP "event loop" 4
+.IX Item "event loop"
+An entity that handles and processes external events and converts them
+into callback invocations.
+.IP "event model" 4
+.IX Item "event model"
+The model used to describe how an event loop handles and processes
+watchers and events.
+.IP "pending" 4
+.IX Item "pending"
+A watcher is pending as soon as the corresponding event has been detected,
+and stops being pending as soon as the watcher will be invoked or its
+pending status is explicitly cleared by the application.
 .Sp
-.Vb 2
+A watcher can be pending, but not active. Stopping a watcher also clears
-\&   #define EV_USE_SELECT 1
+its pending status.
-\&   #define EV_SELECT_IS_WINSOCKET 1   /* forces EV_SELECT_USE_FD_SET, too */
+.IP "real time" 4
-.Ve
+.IX Item "real time"
-.Sp
+The physical time that is observed. It is apparently strictly monotonic :)
-Note that winsockets handling of fd sets is O(n), so you can easily get a
+.IP "wall-clock time" 4
-complexity in the O(nA\*^X) range when using win32.
+.IX Item "wall-clock time"
-.IP "Limited number of file descriptors" 4
+The time and date as shown on clocks. Unlike real time, it can actually
-.IX Item "Limited number of file descriptors"
+be wrong and jump forwards and backwards, e.g. when the you adjust your
-Windows has numerous arbitrary (and low) limits on things.
+clock.
-.Sp
+.IP "watcher" 4
-Early versions of winsocket's select only supported waiting for a maximum
+.IX Item "watcher"
-of \f(CW64\fR handles (probably owning to the fact that all windows kernels
+A data structure that describes interest in certain events. Watchers need
-can only wait for \f(CW64\fR things at the same time internally; Microsoft
+to be started (attached to an event loop) before they can receive events.
-recommends spawning a chain of threads and wait for 63 handles and the
+.IP "watcher invocation" 4
-previous thread in each. Great).
+.IX Item "watcher invocation"
-.Sp
+The act of calling the callback associated with a watcher.
-Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR
-to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select
-call (which might be in libev or elsewhere, for example, perl does its own
-select emulation on windows).
-.Sp
-Another limit is the number of file descriptors in the Microsoft runtime
-libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish
-or something like this inside Microsoft). You can increase this by calling
-\&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another
-arbitrary limit), but is broken in many versions of the Microsoft runtime
-libraries.
-.Sp
-This might get you to about \f(CW512\fR or \f(CW2048\fR sockets (depending on
-windows version and/or the phase of the moon). To get more, you need to
-wrap all I/O functions and provide your own fd management, but the cost of
-calling select (O(nA\*^X)) will likely make this unworkable.
-.SH "PORTABILITY REQUIREMENTS"
-.IX Header "PORTABILITY REQUIREMENTS"
-In addition to a working ISO-C implementation, libev relies on a few
-additional extensions:
-.ie n .IP """void (*)(ev_watcher_type *, int revents)""\fR must have compatible calling conventions regardless of \f(CW""ev_watcher_type *""." 4
-.el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4
-.IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *."
-Libev assumes not only that all watcher pointers have the same internal
-structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also
-assumes that the same (machine) code can be used to call any watcher
-callback: The watcher callbacks have different type signatures, but libev
-calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
-.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4
-.el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4
-.IX Item "sig_atomic_t volatile must be thread-atomic as well"
-The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as
-\&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic w.r.t. accesses from different
-threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is
-believed to be sufficiently portable.
-.ie n .IP """sigprocmask"" must work in a threaded environment" 4
-.el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4
-.IX Item "sigprocmask must work in a threaded environment"
-Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not
-allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical
-pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main
-thread\*(R" or will block signals process-wide, both behaviours would
-be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and
-\&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however.
-.Sp
-The most portable way to handle signals is to block signals in all threads
-except the initial one, and run the default loop in the initial thread as
-well.
-.ie n .IP """long"" must be large enough for common memory allocation sizes" 4
-.el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4
-.IX Item "long must be large enough for common memory allocation sizes"
-To improve portability and simplify using libev, libev uses \f(CW\*(C`long\*(C'\fR
-internally instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On
-non-POSIX systems (Microsoft...) this might be unexpectedly low, but
-is still at least 31 bits everywhere, which is enough for hundreds of
-millions of watchers.
-.ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4
-.el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4
-.IX Item "double must hold a time value in seconds with enough accuracy"
-The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to
-have at least 51 bits of mantissa (and 9 bits of exponent), which is good
-enough for at least into the year 4000. This requirement is fulfilled by
-implementations implementing \s-1IEEE\s0 754 (basically all existing ones).
-.PP
-If you know of other additional requirements drop me a note.
-.SH "COMPILER WARNINGS"
-.IX Header "COMPILER WARNINGS"
-Depending on your compiler and compiler settings, you might get no or a
-lot of warnings when compiling libev code. Some people are apparently
-scared by this.
-.PP
-However, these are unavoidable for many reasons. For one, each compiler
-has different warnings, and each user has different tastes regarding
-warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when
-targeting a specific compiler and compiler-version.
-.PP
-Another reason is that some compiler warnings require elaborate
-workarounds, or other changes to the code that make it less clear and less
-maintainable.
-.PP
-And of course, some compiler warnings are just plain stupid, or simply
-wrong (because they don't actually warn about the condition their message
-seems to warn about).
-.PP
-While libev is written to generate as few warnings as possible,
-\&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev
-with any compiler warnings enabled unless you are prepared to cope with
-them (e.g. by ignoring them). Remember that warnings are just that:
-warnings, not errors, or proof of bugs.
-.SH "VALGRIND"
-.IX Header "VALGRIND"
-Valgrind has a special section here because it is a popular tool that is
-highly useful, but valgrind reports are very hard to interpret.
-.PP
-If you think you found a bug (memory leak, uninitialised data access etc.)
-in libev, then check twice: If valgrind reports something like:
-.PP
-.Vb 3
-\&   ==2274==    definitely lost: 0 bytes in 0 blocks.
-\&   ==2274==      possibly lost: 0 bytes in 0 blocks.
-\&   ==2274==    still reachable: 256 bytes in 1 blocks.
-.Ve
-.PP
-Then there is no memory leak. Similarly, under some circumstances,
-valgrind might report kernel bugs as if it were a bug in libev, or it
-might be confused (it is a very good tool, but only a tool).
-.PP
-If you are unsure about something, feel free to contact the mailing list
-with the full valgrind report and an explanation on why you think this is
-a bug in libev. However, don't be annoyed when you get a brisk \*(L"this is
-no bug\*(R" answer and take the chance of learning how to interpret valgrind
-properly.
-.PP
-If you need, for some reason, empty reports from valgrind for your project
-I suggest using suppression lists.
 .SH "AUTHOR"
 .IX Header "AUTHOR"
-Marc Lehmann <libev@schmorp.de>.
+Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
-.SH "POD ERRORS"
-.IX Header "POD ERRORS"
-Hey! \fBThe above document had some coding errors, which are explained below:\fR
-.IP "Around line 3122:" 4
-.IX Item "Around line 3122:"
-You forgot a '=back' before '=head2'

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Comparing libev/ev.3 (file contents): Revision 1.69 by root, Sat Jul 5 02:25:40 2008 UTC vs. Revision 1.79 by root, Fri Jul 17 14:43:38 2009 UTC

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Comparing libev/ev.3 (file contents):
Revision 1.69 by root, Sat Jul 5 02:25:40 2008 UTC vs.
Revision 1.79 by root, Fri Jul 17 14:43:38 2009 UTC