mirror of
https://github.com/systemd/systemd
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136 lines
6.2 KiB
XML
136 lines
6.2 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+ -->
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<refentry id="sd_event_source_unref" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_event_source_unref</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_unref</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_unref</refname>
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<refname>sd_event_source_unrefp</refname>
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<refname>sd_event_source_ref</refname>
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<refname>sd_event_source_disable_unref</refname>
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<refname>sd_event_source_disable_unrefp</refname>
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<refpurpose>Increase or decrease event source reference counters</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>sd_event_source* <function>sd_event_source_unref</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>sd_event_source_unrefp</function></funcdef>
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<paramdef>sd_event_source **<parameter>source</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_event_source* <function>sd_event_source_disable_unref</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>sd_event_source_disable_unrefp</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_unref()</function> may be used to
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decrement by one the reference counter of the event source object
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specified as <parameter>source</parameter>. The reference counter
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is initially set to one, when the event source is created with calls
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such as
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<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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or
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<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. When
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the reference counter reaches zero it is removed from its event loop
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object and destroyed.</para>
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<para><function>sd_event_source_unrefp()</function> is similar to
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<function>sd_event_source_unref()</function> but takes a pointer to a
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pointer to an <type>sd_event_source</type> object. This call is useful in
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conjunction with GCC's and LLVM's <ulink
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url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
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Variable Attribute</ulink>. Note that this function is defined as
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inline function.</para>
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<para><function>sd_event_source_ref()</function> may be used
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to increase by one the reference counter of the event source object
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specified as <parameter>source</parameter>.</para>
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<para><function>sd_event_source_unref()</function>,
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<function>sd_bus_creds_unrefp()</function> and
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<function>sd_bus_creds_ref()</function> execute no operation if
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the passed event source object is
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<constant>NULL</constant>.</para>
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<para>Note that event source objects stay alive and may be dispatched as long as they have a reference
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counter greater than zero. In order to drop a reference of an event source and make sure the associated
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event source handler function is not called anymore it is recommended to combine a call of
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<function>sd_event_source_unref()</function> with a prior call to
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<function>sd_event_source_set_enabled()</function> with <constant>SD_EVENT_OFF</constant> or call
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<function>sd_event_source_disable_unref()</function>, see below.</para>
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<para><function>sd_event_source_disable_unref()</function> combines a call to
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<function>sd_event_source_set_enabled()</function> with <constant>SD_EVENT_OFF</constant> with
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<function>sd_event_source_unref()</function>. This ensures that the source is disabled before the local
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reference to it is lost. The <parameter>source</parameter> parameter is allowed to be
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<constant>NULL</constant>.</para>
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<para><function>sd_event_source_disable_unrefp()</function> is similar to
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<function>sd_event_source_unrefp()</function>, but in addition disables the source first. This call is
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useful in conjunction with GCC's and LLVM's
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<ulink url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up Variable
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Attribute</ulink>. Note that this function is defined as inline function.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para><function>sd_event_source_unref()</function> and
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<function>sd_event_source_disable_unref()</function> always return <constant>NULL</constant>.
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<function>sd_event_source_ref()</function> always returns the event source object passed in.</para>
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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>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_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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