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3802a3d3 | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
faae655d | 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 | <!-- | |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
b975b0d5 | 8 | This file is part of systemd. |
faae655d | 9 | |
b975b0d5 | 10 | Copyright 2014 Lennart Poettering |
faae655d | 11 | |
b975b0d5 ZJS |
12 | systemd is free software; you can redistribute it and/or modify it |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
faae655d | 16 | |
b975b0d5 ZJS |
17 | systemd is distributed in the hope that it will be useful, but |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
faae655d | 21 | |
b975b0d5 ZJS |
22 | You should have received a copy of the GNU Lesser General Public License |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
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24 | --> |
25 | ||
dc83f27a | 26 | <refentry id="sd_event_new" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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27 | |
28 | <refentryinfo> | |
29 | <title>sd_event_new</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>Developer</contrib> | |
35 | <firstname>Lennart</firstname> | |
36 | <surname>Poettering</surname> | |
37 | <email>lennart@poettering.net</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>sd_event_new</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_event_new</refname> | |
49 | <refname>sd_event_default</refname> | |
50 | <refname>sd_event_ref</refname> | |
51 | <refname>sd_event_unref</refname> | |
4afd3348 | 52 | <refname>sd_event_unrefp</refname> |
dc83f27a LP |
53 | <refname>sd_event_get_tid</refname> |
54 | <refname>sd_event</refname> | |
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55 | |
56 | <refpurpose>Acquire and release an event loop object</refpurpose> | |
57 | </refnamediv> | |
58 | ||
59 | <refsynopsisdiv> | |
60 | <funcsynopsis> | |
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61 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> |
62 | ||
63 | <funcsynopsisinfo><token>typedef</token> struct sd_event sd_event;</funcsynopsisinfo> | |
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64 | |
65 | <funcprototype> | |
66 | <funcdef>int <function>sd_event_new</function></funcdef> | |
dc83f27a | 67 | <paramdef>sd_event **<parameter>event</parameter></paramdef> |
faae655d LP |
68 | </funcprototype> |
69 | ||
70 | <funcprototype> | |
71 | <funcdef>int <function>sd_event_default</function></funcdef> | |
dc83f27a LP |
72 | <paramdef>sd_event **<parameter>event</parameter></paramdef> |
73 | </funcprototype> | |
74 | ||
75 | <funcprototype> | |
76 | <funcdef>sd_event *<function>sd_event_ref</function></funcdef> | |
77 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
faae655d LP |
78 | </funcprototype> |
79 | ||
80 | <funcprototype> | |
dc83f27a LP |
81 | <funcdef>sd_event *<function>sd_event_unref</function></funcdef> |
82 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
faae655d LP |
83 | </funcprototype> |
84 | ||
4afd3348 LP |
85 | <funcprototype> |
86 | <funcdef>void <function>sd_event_unrefp</function></funcdef> | |
87 | <paramdef>sd_event **<parameter>event</parameter></paramdef> | |
88 | </funcprototype> | |
89 | ||
faae655d | 90 | <funcprototype> |
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91 | <funcdef>int <function>sd_event_get_tid</function></funcdef> |
92 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
93 | <paramdef>pid_t *<parameter>tid</parameter></paramdef> | |
faae655d LP |
94 | </funcprototype> |
95 | ||
96 | </funcsynopsis> | |
97 | </refsynopsisdiv> | |
98 | ||
99 | <refsect1> | |
100 | <title>Description</title> | |
101 | ||
102 | <para><function>sd_event_new()</function> allocates a new event | |
103 | loop object. The event loop object is returned in the | |
b8bde116 | 104 | <parameter>event</parameter> parameter. After use, drop |
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105 | the returned reference with |
106 | <function>sd_event_unref()</function>. When the last reference is | |
bfe6c07e | 107 | dropped, the object is freed.</para> |
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108 | |
109 | <para><function>sd_event_default()</function> acquires a reference | |
110 | to the default event loop object of the calling thread, possibly | |
111 | allocating a new object if no default event loop object has been | |
b8bde116 | 112 | allocated yet for the thread. After use, drop the returned |
a6ad1458 | 113 | reference with <function>sd_event_unref()</function>. When the |
b8bde116 | 114 | last reference is dropped, the event loop is freed. If this |
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115 | function is called while the object returned from a previous call |
116 | from the same thread is still referenced, the same object is | |
117 | returned again, but the reference is increased by one. It is | |
118 | recommended to use this call instead of | |
119 | <function>sd_event_new()</function> in order to share event loop | |
120 | objects between various components that are dispatched in the same | |
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121 | thread. All threads have exactly either zero or one default event loop |
122 | objects associated, but never more.</para> | |
faae655d | 123 | |
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124 | <para>After allocating an event loop object, add event sources to |
125 | it with | |
126 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
127 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
128 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
129 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
130 | or | |
131 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
132 | and then execute the event loop using | |
133 | <citerefentry><refentrytitle>sd_event_run</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
134 | ||
faae655d | 135 | <para><function>sd_event_ref()</function> increases the reference |
bfe6c07e | 136 | count of the specified event loop object by one.</para> |
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137 | |
138 | <para><function>sd_event_unref()</function> decreases the | |
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139 | reference count of the specified event loop object by one. If |
140 | the count hits zero, the object is freed. Note that it | |
dca348bc | 141 | is freed regardless of whether it is the default event loop object for a |
faae655d | 142 | thread or not. This means that allocating an event loop with |
b8bde116 | 143 | <function>sd_event_default()</function>, then releasing it, and |
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144 | then acquiring a new one with |
145 | <function>sd_event_default()</function> will result in two | |
b938cb90 | 146 | distinct objects. Note that, in order to free an event loop object, |
faae655d | 147 | all remaining event sources of the event loop also need to be |
bfe6c07e | 148 | freed as each keeps a reference to it.</para> |
dc83f27a | 149 | |
4afd3348 LP |
150 | <para><function>sd_event_unrefp()</function> is similar to |
151 | <function>sd_event_unref()</function> but takes a pointer to a | |
152 | pointer to an <type>sd_event</type> object. This call is useful in | |
153 | conjunction with GCC's and LLVM's <ulink | |
154 | url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up | |
155 | Variable Attribute</ulink>. Note that this function is defined as | |
156 | inline function. Use a declaration like the following, | |
157 | in order to allocate an event loop object that is freed | |
158 | automatically as the code block is left:</para> | |
159 | ||
160 | <programlisting>{ | |
161 | __attribute__((cleanup(sd_event_unrefp)) sd_event *event = NULL; | |
162 | int r; | |
163 | … | |
164 | r = sd_event_default(&event); | |
165 | if (r < 0) | |
166 | fprintf(stderr, "Failed to allocate event loop: %s\n", strerror(-r)); | |
167 | … | |
168 | }</programlisting> | |
169 | ||
170 | <para><function>sd_event_ref()</function>, | |
171 | <function>sd_event_unref()</function> and | |
172 | <function>sd_event_unrefp()</function> execute no operation if the | |
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173 | passed in event loop object is <constant>NULL</constant>.</para> |
174 | ||
175 | <para><function>sd_event_get_tid()</function> retrieves the thread | |
176 | identifier ("TID") of the thread the specified event loop object | |
177 | is associated with. This call is only supported for event loops | |
178 | allocated with <function>sd_event_default()</function>, and | |
179 | returns the identifier for the thread the event loop is the | |
180 | default event loop of. See <citerefentry | |
181 | project='man-pages'><refentrytitle>gettid</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
182 | for more information on thread identifiers.</para> | |
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183 | </refsect1> |
184 | ||
185 | <refsect1> | |
186 | <title>Return Value</title> | |
187 | ||
6d6e4ddd ME |
188 | <para>On success, <function>sd_event_new()</function>, |
189 | <function>sd_event_default()</function> and | |
190 | <function>sd_event_get_tid()</function> return 0 or a positive | |
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191 | integer. On failure, they return a negative errno-style error |
192 | code. <function>sd_event_ref()</function> always returns a pointer | |
193 | to the event loop object passed | |
194 | in. <function>sd_event_unref()</function> always returns | |
bfe6c07e | 195 | <constant>NULL</constant>.</para> |
faae655d LP |
196 | </refsect1> |
197 | ||
198 | <refsect1> | |
199 | <title>Errors</title> | |
200 | ||
201 | <para>Returned errors may indicate the following problems:</para> | |
202 | ||
203 | <variablelist> | |
204 | <varlistentry> | |
8474b70c | 205 | <term><constant>-ENOMEM</constant></term> |
faae655d | 206 | |
bfe6c07e | 207 | <listitem><para>Not enough memory to allocate the object.</para></listitem> |
faae655d LP |
208 | </varlistentry> |
209 | ||
210 | <varlistentry> | |
8474b70c | 211 | <term><constant>-EMFILE</constant></term> |
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212 | |
213 | <listitem><para>The maximum number of event loops has been allocated.</para></listitem> | |
214 | ||
215 | </varlistentry> | |
faae655d | 216 | |
dc83f27a LP |
217 | <varlistentry> |
218 | <term><constant>-ENXIO</constant></term> | |
faae655d | 219 | |
dc83f27a LP |
220 | <listitem><para><function>sd_event_get_tid()</function> was |
221 | invoked on an event loop object that was not allocated with | |
222 | <function>sd_event_default()</function>.</para></listitem> | |
223 | </varlistentry> | |
224 | ||
225 | </variablelist> | |
faae655d LP |
226 | </refsect1> |
227 | ||
dc83f27a LP |
228 | <xi:include href="libsystemd-pkgconfig.xml" /> |
229 | ||
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230 | <refsect1> |
231 | <title>See Also</title> | |
232 | ||
233 | <para> | |
234 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
235 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
236 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
237 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
238 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
239 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
240 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
241 | <citerefentry><refentrytitle>sd_event_add_post</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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242 | <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
243 | <citerefentry><refentrytitle>sd_event_run</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
244 | <citerefentry project='man-pages'><refentrytitle>gettid</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
faae655d LP |
245 | </para> |
246 | </refsect1> | |
247 | ||
248 | </refentry> |