--- /dev/null
+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+ This file is part of elogind.
+
+ Copyright 2015 Lennart Poettering
+
+ elogind is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ elogind is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with elogind; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_event_source_set_priority" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_event_source_set_priority</title>
+ <productname>elogind</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_event_source_set_priority</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_event_source_set_priority</refname>
+ <refname>sd_event_source_get_priority</refname>
+ <refname>SD_EVENT_PRIORITY_IMPORTANT</refname>
+ <refname>SD_EVENT_PRIORITY_NORMAL</refname>
+ <refname>SD_EVENT_PRIORITY_IDLE</refname>
+
+ <refpurpose>Set or retrieve the priority of event sources</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <elogind/sd-event.h></funcsynopsisinfo>
+
+ <funcsynopsisinfo><token>enum</token> {
+ <constant>SD_EVENT_SOURCE_IMPORTANT</constant> = -100,
+ <constant>SD_EVENT_SOURCE_NORMAL</constant> = 0,
+ <constant>SD_EVENT_SOURCE_IDLE</constant> = 100,
+};</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_set_priority</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>int64_t <parameter>priority</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_priority</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>int64_t *<parameter>priority</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_event_source_set_priority()</function> may be
+ used to set the priority for the event source object specified as
+ <parameter>source</parameter>. The priority is specified as an
+ arbitrary signed 64bit integer. The priority is initialized to
+ <constant>SD_EVENT_PRIORITY_NORMAL</constant> (0) when the event
+ source is allocated with a call such as
+ <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ or
+ <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ and may be changed with this call. If multiple event sources have seen events at the same time, they are dispatched in the order indicated by the
+ event sources' priorities. Event sources with smaller priority
+ values are dispatched first. As well-known points of reference,
+ the constants <constant>SD_EVENT_PRIORITY_IMPORTANT</constant>
+ (-100), <constant>SD_EVENT_PRIORITY_NORMAL</constant> (0) and
+ <constant>SD_EVENT_PRIORITY_IDLE</constant> (100) may be used to
+ indicate event sources that shall be dispatched early, normally or
+ late. It is recommended to specify priorities based on these
+ definitions, and relative to them -- however, the full 64bit
+ signed integer range is available for ordering event
+ sources.</para>
+
+ <para>Priorities define the order in which event sources that have
+ seen events are dispatched. Care should be taken to ensure that
+ high-priority event sources (those with negative priority values
+ assigned) do not cause starvation of low-priority event sources
+ (those with positive priority values assigned).</para>
+
+ <para>The order in which event sources with the same priority are
+ dispatched is undefined, but the event loop generally tries to
+ dispatch them in the order it learnt about events on them. As the
+ backing kernel primitives do not provide accurate information
+ about the order in which events occured this is not necessarily
+ reliable. However, it is guaranteed that if events are seen on
+ multiple same-priority event sources at the same time, each one is
+ not dispatched again until all others have been dispatched
+ once. This behaviour guarantees that within each priority
+ particular event sources do not starve or dominate the event
+ loop.</para>
+
+ <para><function>sd_event_source_get_priority()</function> may be
+ used to query the current priority assigned to the event source
+ object <parameter>source</parameter>.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success,
+ <function>sd_event_source_set_priority()</function> and
+ <function>sd_event_source_get_priority()</function> return a
+ non-negative integer. On failure, they return a negative
+ errno-style error code.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para><parameter>source</parameter> is not a valid
+ pointer to an <structname>sd_event_source</structname>
+ object.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ENOMEM</constant></term>
+
+ <listitem><para>Not enough memory.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ESTALE</constant></term>
+
+ <listitem><para>The event loop is already terminated.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ECHILD</constant></term>
+
+ <listitem><para>The event loop has been created in a different process.</para></listitem>
+
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
+ <xi:include href="libelogind-pkgconfig.xml" />
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>
~ianmdlvl / elogind.git / blobdiff