mirror of
https://github.com/systemd/systemd.git
synced 2024-12-27 07:22:31 +03:00
173 lines
7.1 KiB
XML
173 lines
7.1 KiB
XML
<?xml version='1.0'?>
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
|
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
|
|
|
|
<refentry id="sd_event_source_set_priority" xmlns:xi="http://www.w3.org/2001/XInclude">
|
|
|
|
<refentryinfo>
|
|
<title>sd_event_source_set_priority</title>
|
|
<productname>systemd</productname>
|
|
</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 <systemd/sd-event.h></funcsynopsisinfo>
|
|
|
|
<funcsynopsisinfo><token>enum</token> {
|
|
<constant>SD_EVENT_PRIORITY_IMPORTANT</constant> = -100,
|
|
<constant>SD_EVENT_PRIORITY_NORMAL</constant> = 0,
|
|
<constant>SD_EVENT_PRIORITY_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 64-bit 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 64-bit
|
|
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 occurred 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 behavior guarantees that within each priority
|
|
particular event sources do not starve or dominate the event
|
|
loop.</para>
|
|
|
|
<para>The priority of event sources may be changed at any time of their lifetime, with the exception of inotify
|
|
event sources (i.e. those created with
|
|
<citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>) whose
|
|
priority may only be changed in the time between their initial creation and the first subsequent event loop
|
|
iteration.</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>
|
|
|
|
<refsect2>
|
|
<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, library or module instance.</para></listitem>
|
|
|
|
</varlistentry>
|
|
|
|
</variablelist>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<xi:include href="libsystemd-pkgconfig.xml" />
|
|
|
|
<refsect1>
|
|
<title>History</title>
|
|
<para><function>sd_event_source_set_priority()</function> and
|
|
<function>sd_event_source_get_priority()</function> were added in version 229.</para>
|
|
</refsect1>
|
|
|
|
<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_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|