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3802a3d3 | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
4dfefc19 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
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6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
b975b0d5 | 8 | This file is part of systemd. |
4dfefc19 | 9 | |
b975b0d5 | 10 | Copyright 2014 Zbigniew Jędrzejewski-Szmek |
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11 | --> |
12 | ||
dc83f27a | 13 | <refentry id="sd_event_add_defer" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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14 | |
15 | <refentryinfo> | |
16 | <title>sd_event_add_defer</title> | |
17 | <productname>systemd</productname> | |
18 | ||
19 | <authorgroup> | |
20 | <author> | |
21 | <contrib>More text</contrib> | |
22 | <firstname>Zbigniew</firstname> | |
23 | <surname>Jędrzejewski-Szmek</surname> | |
24 | <email>zbyszek@in.waw.pl</email> | |
25 | </author> | |
26 | </authorgroup> | |
27 | </refentryinfo> | |
28 | ||
29 | <refmeta> | |
30 | <refentrytitle>sd_event_add_defer</refentrytitle> | |
31 | <manvolnum>3</manvolnum> | |
32 | </refmeta> | |
33 | ||
34 | <refnamediv> | |
35 | <refname>sd_event_add_defer</refname> | |
36 | <refname>sd_event_add_post</refname> | |
37 | <refname>sd_event_add_exit</refname> | |
dc83f27a | 38 | <refname>sd_event_handler_t</refname> |
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39 | |
40 | <refpurpose>Add static event sources to an event loop</refpurpose> | |
41 | </refnamediv> | |
42 | ||
43 | <refsynopsisdiv> | |
44 | <funcsynopsis> | |
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45 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> |
46 | ||
47 | <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo> | |
48 | ||
49 | <funcprototype> | |
50 | <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef> | |
51 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
52 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
53 | </funcprototype> | |
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54 | |
55 | <funcprototype> | |
56 | <funcdef>int <function>sd_event_add_defer</function></funcdef> | |
57 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
58 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
59 | <paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef> | |
60 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
61 | </funcprototype> | |
62 | ||
63 | <funcprototype> | |
64 | <funcdef>int <function>sd_event_add_post</function></funcdef> | |
65 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
66 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
67 | <paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef> | |
68 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
69 | </funcprototype> | |
70 | ||
71 | <funcprototype> | |
72 | <funcdef>int <function>sd_event_add_exit</function></funcdef> | |
73 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
74 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
75 | <paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef> | |
76 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
77 | </funcprototype> | |
78 | ||
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79 | </funcsynopsis> |
80 | </refsynopsisdiv> | |
81 | ||
82 | <refsect1> | |
83 | <title>Description</title> | |
84 | ||
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85 | <para>These three functions add new static event sources to an |
86 | event loop. The event loop object is specified in the | |
87 | <parameter>event</parameter> parameter, the event source object is | |
88 | returned in the <parameter>source</parameter> parameter. The event | |
89 | sources are enabled statically and will "fire" when the event loop | |
90 | is run and the conditions described below are met. The handler | |
91 | function will be passed the <parameter>userdata</parameter> | |
92 | pointer, which may be chosen freely by the caller.</para> | |
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93 | |
94 | <para><function>sd_event_add_defer()</function> adds a new event | |
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95 | source that will be dispatched instantly, before the event loop |
96 | goes to sleep again and waits for new events. By default, the | |
97 | handler will be called once | |
98 | (<constant>SD_EVENT_ONESHOT</constant>). Note that if the event | |
99 | source is set to <constant>SD_EVENT_ON</constant> the event loop | |
7f3fdb7f | 100 | will never go to sleep again, but continuously call the handler, |
dc83f27a | 101 | possibly interleaved with other event sources.</para> |
4dfefc19 | 102 | |
f49481d0 | 103 | <para><function>sd_event_add_post()</function> adds a new event |
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104 | source that is run before the event loop will sleep and wait |
105 | for new events, but only after at least one other non-post event | |
106 | source was dispatched. By default, the source is enabled | |
107 | permanently (<constant>SD_EVENT_ON</constant>). Note that this | |
108 | event source type will still allow the event loop to go to sleep | |
109 | again, even if set to <constant>SD_EVENT_ON</constant>, as long as | |
110 | no other event source is ever triggered.</para> | |
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111 | |
112 | <para><function>sd_event_add_exit()</function> adds a new event | |
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113 | source that will be dispatched when the event loop is terminated |
114 | with <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
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115 | |
116 | <para>The | |
117 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
118 | function may be used to enable the event source permanently | |
119 | (<constant>SD_EVENT_ON</constant>) or to make it fire just once | |
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120 | (<constant>SD_EVENT_ONESHOT</constant>).</para> |
121 | ||
122 | <para>If the handler function returns a negative error code, it | |
123 | will be disabled after the invocation, even if the | |
124 | <constant>SD_EVENT_ON</constant> mode was requested before.</para> | |
125 | ||
126 | <para>To destroy an event source object use | |
127 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
128 | but note that the event source is only removed from the event loop | |
129 | when all references to the event source are dropped. To make sure | |
130 | an event source does not fire anymore, even when there's still a | |
131 | reference to it kept, consider setting the event source to | |
132 | <constant>SD_EVENT_OFF</constant> with | |
133 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
134 | ||
135 | <para>If the second parameter of these functions is passed as | |
136 | NULL no reference to the event source object is returned. In this | |
137 | case the event source is considered "floating", and will be | |
138 | destroyed implicitly when the event loop itself is | |
139 | destroyed.</para> | |
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140 | </refsect1> |
141 | ||
142 | <refsect1> | |
143 | <title>Return Value</title> | |
144 | ||
06bf09af | 145 | <para>On success, these functions return 0 or a positive |
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146 | integer. On failure, they return a negative errno-style error |
147 | code.</para> | |
148 | </refsect1> | |
149 | ||
150 | <refsect1> | |
151 | <title>Errors</title> | |
152 | ||
153 | <para>Returned errors may indicate the following problems:</para> | |
154 | ||
155 | <variablelist> | |
156 | <varlistentry> | |
8474b70c | 157 | <term><constant>-ENOMEM</constant></term> |
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158 | |
159 | <listitem><para>Not enough memory to allocate an object.</para></listitem> | |
160 | </varlistentry> | |
161 | ||
162 | <varlistentry> | |
8474b70c | 163 | <term><constant>-EINVAL</constant></term> |
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164 | |
165 | <listitem><para>An invalid argument has been passed.</para></listitem> | |
166 | </varlistentry> | |
167 | ||
168 | <varlistentry> | |
8474b70c | 169 | <term><constant>-ESTALE</constant></term> |
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170 | |
171 | <listitem><para>The event loop is already terminated.</para></listitem> | |
172 | </varlistentry> | |
173 | ||
174 | <varlistentry> | |
8474b70c | 175 | <term><constant>-ECHILD</constant></term> |
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176 | |
177 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
178 | </varlistentry> | |
179 | ||
180 | </variablelist> | |
181 | </refsect1> | |
182 | ||
dc83f27a | 183 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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184 | |
185 | <refsect1> | |
186 | <title>See Also</title> | |
187 | ||
188 | <para> | |
189 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
190 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
191 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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192 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
193 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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194 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
195 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
196 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
1eb54dc6 | 197 | <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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198 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
199 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
200 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
201 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
202 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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203 | </para> |
204 | </refsect1> | |
205 | ||
206 | </refentry> |