mirror of
https://github.com/systemd/systemd.git
synced 2024-12-26 03:22:00 +03:00
214 lines
8.3 KiB
XML
214 lines
8.3 KiB
XML
<?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 systemd.
|
||
|
||
Copyright 2015 Zbigniew Jędrzejewski-Szmek
|
||
|
||
systemd 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.
|
||
|
||
systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
|
||
-->
|
||
|
||
<refentry id="sd_event_wait" conditional="ENABLE_KDBUS">
|
||
|
||
<refentryinfo>
|
||
<title>sd_event_wait</title>
|
||
<productname>systemd</productname>
|
||
|
||
<authorgroup>
|
||
<author>
|
||
<contrib>Developer</contrib>
|
||
<firstname>Tom</firstname>
|
||
<surname>Gundersen</surname>
|
||
<email>teg@jklm.no</email>
|
||
</author>
|
||
</authorgroup>
|
||
</refentryinfo>
|
||
|
||
<refmeta>
|
||
<refentrytitle>sd_event_wait</refentrytitle>
|
||
<manvolnum>3</manvolnum>
|
||
</refmeta>
|
||
|
||
<refnamediv>
|
||
<refname>sd_event_wait</refname>
|
||
<refname>sd_event_prepare</refname>
|
||
<refname>sd_event_dispatch</refname>
|
||
|
||
<refpurpose>Run parts of libsystemd event loop</refpurpose>
|
||
</refnamediv>
|
||
|
||
<refsynopsisdiv>
|
||
<funcsynopsis>
|
||
<funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_event_prepare</function></funcdef>
|
||
<paramdef>sd_event *<parameter>event</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_event_wait</function></funcdef>
|
||
<paramdef>sd_event *<parameter>event</parameter></paramdef>
|
||
<paramdef>uint64_t <parameter>timeout</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
<funcprototype>
|
||
<funcdef>int <function>sd_event_dispatch</function></funcdef>
|
||
<paramdef>sd_event *<parameter>event</parameter></paramdef>
|
||
</funcprototype>
|
||
|
||
</funcsynopsis>
|
||
</refsynopsisdiv>
|
||
|
||
<refsect1>
|
||
<title>Description</title>
|
||
|
||
<para>Functions described here form parts of an event loop.</para>
|
||
|
||
<para><function>sd_event_prepare</function> checks for pending
|
||
events and arms necessary timers. If any events are ready to be
|
||
processed, it returns a positive value, and the events should be
|
||
processed with <function>sd_event_dispatch</function>.
|
||
<function>sd_event_dispatch</function> runs a handler for one of
|
||
the events from the sources with the highest priority. On success,
|
||
<function>sd_event_dispatch</function> returns either 0, which
|
||
means that the loop is finished, or a positive value, which means
|
||
that the loop is again in the initial state and
|
||
<function>sd_event_prepare</function> should be called again.
|
||
</para>
|
||
|
||
<para>In case <function>sd_event_prepare</function> returned 0,
|
||
<function>sd_event_wait</function> should be called to wait for
|
||
events or a timeout. If any events are ready to be processed, it
|
||
returns a positive value, and the events should be processed with
|
||
<function>sd_event_dispatch</function>. Otherwise, the loop is
|
||
back in the inital state and <function>sd_event_prepare</function>
|
||
should be called again.</para>
|
||
|
||
<programlisting>
|
||
┌──────────┐
|
||
│ initial ├──←←←←←←←←←←←←←←←←←←←─┐
|
||
└───┬──────┘ ↑
|
||
│ ↑
|
||
sd_event_prepare ┌─────────┐ ↑
|
||
├ 0 →→→→→→→──┤ armed │ ↑
|
||
1 └───┬─────┘ ↑
|
||
↓ │ ↑
|
||
↓ sd_event_wait ↑
|
||
├───←←←←←←←─── 1 ┴─ 0 →→→→→→→─┘
|
||
┌───┴──────┐ ↑
|
||
│ pending │ ↑
|
||
└───┬──────┘ ↑
|
||
│ ↑
|
||
sd_event_dispatch ↑
|
||
↓ ↑
|
||
├ 1 ──────────→→→→→→→─────────┘
|
||
0
|
||
↓
|
||
┌───┴──────┐
|
||
│ finished │
|
||
└──────────┘
|
||
</programlisting>
|
||
|
||
<para>All three functions as the first argument take the event
|
||
loop object <parameter>event</parameter> that is created with with
|
||
<function>sd_event_new</function>. The timeout for
|
||
<function>sd_event_wait</function> is specified with
|
||
<parameter>timeout</parameter> in milliseconds.
|
||
<constant>(uint64_t) -1</constant> may be used to specify an
|
||
infinite timeout.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Return Value</title>
|
||
|
||
<para>On success, these functions return 0 or a positive integer.
|
||
On failure, they return a negative errno-style error code. In case
|
||
of <function>sd_event_prepare</function> and
|
||
<function>sd_event_wait</function> a positive value means that
|
||
events are ready to be processed and 0 means that no events are
|
||
ready. In case of <function>sd_event_dispatch</function> a
|
||
positive value means that the loop is again in the initial state
|
||
and 0 means the loop is finished. For any of those functions, a
|
||
negative return value means the loop must be aborted.</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 <parameter>event</parameter> is
|
||
<constant>NULL</constant>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><constant>-EBUSY</constant></term>
|
||
|
||
<listitem><para>The event loop object is not in the right
|
||
state.</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>
|
||
|
||
<para>Other errors are possible too.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Notes</title>
|
||
|
||
<para>Functions described here are available
|
||
as a shared library, which can be compiled and linked to with the
|
||
<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
||
file.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>See Also</title>
|
||
|
||
<para>
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_run</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_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>sd_event_add_post</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
||
</para>
|
||
</refsect1>
|
||
|
||
</refentry>
|