]>
Commit | Line | Data |
---|---|---|
0bca2831 LP |
1 | <?xml version='1.0'?> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> | |
5 | ||
6 | <refentry id="sd_event_source_set_floating" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
7 | ||
8 | <refentryinfo> | |
9 | <title>sd_event_source_set_floating</title> | |
10 | <productname>systemd</productname> | |
11 | </refentryinfo> | |
12 | ||
13 | <refmeta> | |
14 | <refentrytitle>sd_event_source_set_floating</refentrytitle> | |
15 | <manvolnum>3</manvolnum> | |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
19 | <refname>sd_event_source_set_floating</refname> | |
20 | <refname>sd_event_source_get_floating</refname> | |
21 | ||
22 | <refpurpose>Set or retrieve 'floating' state of event sources</refpurpose> | |
23 | </refnamediv> | |
24 | ||
25 | <refsynopsisdiv> | |
26 | <funcsynopsis> | |
27 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
28 | ||
29 | <funcprototype> | |
30 | <funcdef>int <function>sd_event_source_set_floating</function></funcdef> | |
31 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
32 | <paramdef>int <parameter>floating</parameter></paramdef> | |
33 | </funcprototype> | |
34 | ||
35 | <funcprototype> | |
36 | <funcdef>int <function>sd_event_source_get_floating</function></funcdef> | |
37 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
38 | </funcprototype> | |
39 | ||
40 | </funcsynopsis> | |
41 | </refsynopsisdiv> | |
42 | ||
43 | <refsect1> | |
44 | <title>Description</title> | |
45 | ||
46 | <para><function>sd_event_source_set_floating()</function> takes a boolean and sets the 'floating' state | |
47 | of the specified event source object. This is used to change the direction of reference counts for the | |
48 | object and the event loop it is associated with. In non-floating mode, the event source object holds a | |
49 | reference to the event loop object, but not vice versa. The creator of the event source object must hold | |
50 | a reference to it as long as the source should exist. In floating mode, the event loop holds a reference | |
51 | to the source object, and will decrease the reference count when being freed. This means that a reference | |
52 | to the event loop should be held to prevent both from being destroyed.</para> | |
53 | ||
54 | <para>Various calls that allocate event source objects (i.e. | |
55 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
56 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry> and | |
57 | similar) will automatically set an event source object to 'floating' mode if the caller passed | |
58 | <constant>NULL</constant> in the parameter used to return a reference to the event source object. | |
59 | Nevertheless, it may be necessary to gain temporary access to the source object, for example to adjust | |
60 | event source properties after allocation (e.g. its priority or description string). In those cases the | |
61 | object may be created in non-floating mode, and the returned reference used to adjust the properties, and | |
62 | the object marked as floating afterwards, and the reference in the caller dropped.</para> | |
63 | ||
64 | <para><function>sd_event_source_get_floating()</function> may be used to query the current 'floating' | |
65 | state of the event source object <parameter>source</parameter>. It returns zero if 'floating' mode is | |
66 | off, positive if it is on.</para> | |
67 | </refsect1> | |
68 | ||
69 | <refsect1> | |
70 | <title>Return Value</title> | |
71 | ||
72 | <para>On success, <function>sd_event_source_set_floating()</function> and | |
73 | <function>sd_event_source_get_floating()</function> return a non-negative integer. On failure, they | |
74 | return a negative errno-style error code.</para> | |
75 | ||
76 | <refsect2> | |
77 | <title>Errors</title> | |
78 | ||
79 | <para>Returned errors may indicate the following problems:</para> | |
80 | ||
81 | <variablelist> | |
82 | <varlistentry> | |
83 | <term><constant>-EINVAL</constant></term> | |
84 | ||
85 | <listitem><para><parameter>source</parameter> is not a valid pointer to an | |
86 | <structname>sd_event_source</structname> object.</para></listitem> | |
87 | </varlistentry> | |
88 | ||
89 | <varlistentry> | |
90 | <term><constant>-ECHILD</constant></term> | |
91 | ||
92 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
93 | ||
94 | </varlistentry> | |
95 | ||
96 | </variablelist> | |
97 | </refsect2> | |
98 | </refsect1> | |
99 | ||
100 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
101 | ||
102 | <refsect1> | |
103 | <title>See Also</title> | |
104 | ||
105 | <para> | |
106 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
107 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
108 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
109 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
110 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
111 | <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
112 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
113 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
114 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
115 | </para> | |
116 | </refsect1> | |
117 | ||
118 | </refentry> |