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129 lines
5.6 KiB
XML
129 lines
5.6 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_event_source_set_floating" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_event_source_set_floating</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_event_source_set_floating</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_event_source_set_floating</refname>
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<refname>sd_event_source_get_floating</refname>
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<refpurpose>Set or retrieve 'floating' state of event sources</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_event_source_set_floating</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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<paramdef>int <parameter>floating</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_source_get_floating</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_event_source_set_floating()</function> takes a boolean and sets the 'floating' state
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of the specified event source object. This is used to change the direction of reference counts for the
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object and the event loop it is associated with. In non-floating mode, the event source object holds a
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reference to the event loop object, but not vice versa. The creator of the event source object must hold
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a reference to it as long as the source should exist. In floating mode, the event loop holds a reference
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to the source object, and will decrease the reference count when being freed. This means that a reference
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to the event loop should be held to prevent both from being destroyed.</para>
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<para>Various calls that allocate event source objects (i.e.
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<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
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similar) will automatically set an event source object to 'floating' mode if the caller passed
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<constant>NULL</constant> in the parameter used to return a reference to the event source object.
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Nevertheless, it may be necessary to gain temporary access to the source object, for example to adjust
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event source properties after allocation (e.g. its priority or description string). In those cases the
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object may be created in non-floating mode, and the returned reference used to adjust the properties, and
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the object marked as floating afterwards, and the reference in the caller dropped.</para>
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<para><function>sd_event_source_get_floating()</function> may be used to query the current 'floating'
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state of the event source object <parameter>source</parameter>. It returns zero if 'floating' mode is
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off, positive if it is on.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, <function>sd_event_source_set_floating()</function> and
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<function>sd_event_source_get_floating()</function> return a non-negative integer. On failure, they
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return a negative errno-style error code.</para>
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<refsect2>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para><parameter>source</parameter> is not a valid pointer to an
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<structname>sd_event_source</structname> object.</para>
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<xi:include href="version-info.xml" xpointer="v244"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The event loop has been created in a different process, library or module instance.</para>
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<xi:include href="version-info.xml" xpointer="v244"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>History</title>
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<para><function>sd_event_source_set_floating()</function> and
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<function>sd_event_source_get_floating()</function> were added in version 244.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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