mirror of
https://github.com/systemd/systemd-stable.git
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11a1589223
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
206 lines
8.6 KiB
XML
206 lines
8.6 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2014 Zbigniew Jędrzejewski-Szmek
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-->
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<refentry id="sd_event_add_defer" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_event_add_defer</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>More text</contrib>
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<firstname>Zbigniew</firstname>
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<surname>Jędrzejewski-Szmek</surname>
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<email>zbyszek@in.waw.pl</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_event_add_defer</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_add_defer</refname>
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<refname>sd_event_add_post</refname>
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<refname>sd_event_add_exit</refname>
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<refname>sd_event_handler_t</refname>
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<refpurpose>Add static event sources to an event loop</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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<funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
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<funcprototype>
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<funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef>
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<paramdef>sd_event_source *<parameter>s</parameter></paramdef>
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<paramdef>void *<parameter>userdata</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_add_defer</function></funcdef>
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<paramdef>sd_event *<parameter>event</parameter></paramdef>
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<paramdef>sd_event_source **<parameter>source</parameter></paramdef>
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<paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef>
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<paramdef>void *<parameter>userdata</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_add_post</function></funcdef>
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<paramdef>sd_event *<parameter>event</parameter></paramdef>
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<paramdef>sd_event_source **<parameter>source</parameter></paramdef>
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<paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef>
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<paramdef>void *<parameter>userdata</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_add_exit</function></funcdef>
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<paramdef>sd_event *<parameter>event</parameter></paramdef>
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<paramdef>sd_event_source **<parameter>source</parameter></paramdef>
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<paramdef>sd_event_handler_t <parameter>handler</parameter></paramdef>
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<paramdef>void *<parameter>userdata</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>These three functions add new static event sources to an
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event loop. The event loop object is specified in the
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<parameter>event</parameter> parameter, the event source object is
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returned in the <parameter>source</parameter> parameter. The event
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sources are enabled statically and will "fire" when the event loop
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is run and the conditions described below are met. The handler
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function will be passed the <parameter>userdata</parameter>
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pointer, which may be chosen freely by the caller.</para>
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<para><function>sd_event_add_defer()</function> adds a new event
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source that will be dispatched instantly, before the event loop
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goes to sleep again and waits for new events. By default, the
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handler will be called once
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(<constant>SD_EVENT_ONESHOT</constant>). Note that if the event
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source is set to <constant>SD_EVENT_ON</constant> the event loop
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will never go to sleep again, but continuously call the handler,
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possibly interleaved with other event sources.</para>
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<para><function>sd_event_add_post()</function> adds a new event
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source that is run before the event loop will sleep and wait
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for new events, but only after at least one other non-post event
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source was dispatched. By default, the source is enabled
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permanently (<constant>SD_EVENT_ON</constant>). Note that this
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event source type will still allow the event loop to go to sleep
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again, even if set to <constant>SD_EVENT_ON</constant>, as long as
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no other event source is ever triggered.</para>
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<para><function>sd_event_add_exit()</function> adds a new event
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source that will be dispatched when the event loop is terminated
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with <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para>The
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<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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function may be used to enable the event source permanently
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(<constant>SD_EVENT_ON</constant>) or to make it fire just once
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(<constant>SD_EVENT_ONESHOT</constant>).</para>
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<para>If the handler function returns a negative error code, it
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will be disabled after the invocation, even if the
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<constant>SD_EVENT_ON</constant> mode was requested before.</para>
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<para>To destroy an event source object use
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<citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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but note that the event source is only removed from the event loop
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when all references to the event source are dropped. To make sure
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an event source does not fire anymore, even when there's still a
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reference to it kept, consider setting the event source to
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<constant>SD_EVENT_OFF</constant> with
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<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para>If the second parameter of these functions is passed as
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NULL no reference to the event source object is returned. In this
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case the event source is considered "floating", and will be
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destroyed implicitly when the event loop itself is
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destroyed.</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, these functions return 0 or a positive
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integer. On failure, they return a negative errno-style error
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code.</para>
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</refsect1>
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<refsect1>
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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>-ENOMEM</constant></term>
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<listitem><para>Not enough memory to allocate an object.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>An invalid argument has been passed.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ESTALE</constant></term>
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<listitem><para>The event loop is already terminated.</para></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.</para></listitem>
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</varlistentry>
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</variablelist>
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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>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_now</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_source_set_enabled</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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<citerefentry><refentrytitle>sd_event_source_set_userdata</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_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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