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1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | ||
5 | <!-- | |
6 | This file is part of systemd. | |
7 | ||
8 | Copyright 2015 Lennart Poettering | |
9 | ||
10 | systemd is free software; you can redistribute it and/or modify it | |
11 | under the terms of the GNU Lesser General Public License as published by | |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
13 | (at your option) any later version. | |
14 | ||
15 | systemd is distributed in the hope that it will be useful, but | |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
18 | Lesser General Public License for more details. | |
19 | ||
20 | You should have received a copy of the GNU Lesser General Public License | |
21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
22 | --> | |
23 | ||
24 | <refentry id="sd-event" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
25 | ||
26 | <refentryinfo> | |
27 | <title>sd-event</title> | |
28 | <productname>systemd</productname> | |
29 | ||
30 | <authorgroup> | |
31 | <author> | |
32 | <contrib>Developer</contrib> | |
33 | <firstname>Lennart</firstname> | |
34 | <surname>Poettering</surname> | |
35 | <email>lennart@poettering.net</email> | |
36 | </author> | |
37 | </authorgroup> | |
38 | </refentryinfo> | |
39 | ||
40 | <refmeta> | |
41 | <refentrytitle>sd-event</refentrytitle> | |
42 | <manvolnum>3</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd-event</refname> | |
47 | <refpurpose>A generic event loop implementation</refpurpose> | |
48 | </refnamediv> | |
49 | ||
50 | <refsynopsisdiv> | |
51 | <funcsynopsis> | |
52 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
53 | </funcsynopsis> | |
54 | ||
55 | <cmdsynopsis> | |
56 | <command>pkg-config --cflags --libs libsystemd</command> | |
57 | </cmdsynopsis> | |
58 | ||
59 | </refsynopsisdiv> | |
60 | ||
61 | <refsect1> | |
62 | <title>Description</title> | |
63 | ||
64 | <para><filename>sd-event.h</filename> provides a generic event | |
65 | loop implementation, based on Linux <citerefentry | |
66 | project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>. | |
67 | </para> | |
68 | ||
69 | <para>See | |
70 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
71 | <citerefentry><refentrytitle>sd_event_run</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
72 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
73 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
74 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
75 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
76 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
77 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
78 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
79 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
80 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
81 | <citerefentry><refentrytitle>sd_event_source_get_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
82 | <citerefentry><refentrytitle>sd_event_source_get_pending</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
83 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
84 | <citerefentry><refentrytitle>sd_event_source_set_prepare</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
85 | <citerefentry><refentrytitle>sd_event_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
86 | <citerefentry><refentrytitle>sd_event_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
87 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
88 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
89 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
90 | for more information about the functions available.</para> | |
91 | ||
92 | <para>The event loop design is targeted on running a separate | |
93 | instance of the event loop in each thread; it has no concept of | |
94 | distributing events from a single event loop instance onto | |
95 | multiple worker threads. Dispatching events is strictly ordered | |
96 | and subject to configurable priorities. In each event loop | |
97 | iteration a single event source is dispatched. Each time an event | |
98 | source is dispatched the kernel is polled for new events, before | |
99 | the next event source is dispatched. The event loop is designed to | |
2dd67817 | 100 | honor priorities and provide fairness within each priority. It is |
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101 | not designed to provide optimal throughput, as this contradicts |
102 | these goals due the limitations of the underlying <citerefentry | |
103 | project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
104 | primitives.</para> | |
105 | ||
106 | <para>The event loop implementation provides the following features:</para> | |
107 | ||
108 | <orderedlist> | |
109 | <listitem><para>I/O event sources, based on <citerefentry | |
110 | project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>'s | |
111 | file descriptor watching, including edge triggered events (<constant>EPOLLET</constant>). See <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
112 | ||
113 | <listitem><para>Timer event sources, based on <citerefentry | |
114 | project='man-pages'><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
115 | supporting the <constant>CLOCK_MONOTONIC</constant>, | |
116 | <constant>CLOCK_REALTIME</constant>, | |
117 | <constant>CLOCK_BOOTIME</constant> clocks, as well as the | |
118 | <constant>CLOCK_REALTIME_ALARM</constant> and | |
119 | <constant>CLOCK_BOOTTIME_ALARM</constant> clocks that can resume | |
120 | the system from suspend. When creating timer events a required | |
121 | accuracy parameter may be specified which allows coalescing of | |
122 | timer events to minimize power consumption. See <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
123 | ||
124 | <listitem><para>UNIX process signal events, based on | |
125 | <citerefentry | |
126 | project='man-pages'><refentrytitle>signalfd</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
127 | including full support for real-time signals, and queued parameters. See <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
128 | ||
129 | <listitem><para>Child process state change events, based on | |
130 | <citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>. See <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
131 | ||
132 | <listitem><para>Static event sources, of three types: defer, | |
133 | post and exit, for invoking calls in each event loop, after | |
134 | other event sources or at event loop termination. See | |
135 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
136 | ||
137 | <listitem><para>Event sources may be assigned a 64bit priority | |
138 | value, that controls the order in which event sources are | |
7f3fdb7f | 139 | dispatched if multiple are pending simultaneously. See |
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140 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> |
141 | ||
142 | <listitem><para>The event loop may automatically send watchdog | |
143 | notification messages to the service manager. See | |
144 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem> | |
145 | ||
146 | <listitem><para>The event loop may be integrated into foreign | |
147 | event loops, such as the GLib one. See | |
148 | <citerefentry><refentrytitle>sd_event_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
149 | for an example.</para></listitem> | |
150 | </orderedlist> | |
151 | ||
152 | </refsect1> | |
153 | ||
154 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
155 | ||
156 | <refsect1> | |
157 | <title>See Also</title> | |
158 | <para> | |
159 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
160 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
161 | <citerefentry><refentrytitle>sd_event_run</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
162 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
163 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
164 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
165 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
166 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
167 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
168 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
169 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
170 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
171 | <citerefentry><refentrytitle>sd_event_source_get_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
172 | <citerefentry><refentrytitle>sd_event_source_get_pending</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
173 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
174 | <citerefentry><refentrytitle>sd_event_source_set_prepare</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
175 | <citerefentry><refentrytitle>sd_event_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
176 | <citerefentry><refentrytitle>sd_event_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
177 | <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
178 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
179 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
180 | <citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
181 | <citerefentry project='man-pages'><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
182 | <citerefentry project='man-pages'><refentrytitle>signalfd</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
183 | <citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
184 | </para> | |
185 | </refsect1> | |
186 | ||
187 | </refentry> |