--- /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 systemd.
+
+ Copyright 2015 Lennart Poettering
+
+ 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_set_watchdog" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_event_set_watchdog</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_event_set_watchdog</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_event_set_watchdog</refname>
+ <refname>sd_event_get_watchdog</refname>
+
+ <refpurpose>Enable event loop watchdog support</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_set_watchdog</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ <paramdef>int b</paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_get_watchdog</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_event_set_watchdog()</function> may be used to
+ enable or disable automatic watchdog notification support in the
+ event loop object specified in the <parameter>event</parameter>
+ parameter. Specifically, depending on the <parameter>b</parameter>
+ boolean argument this will make sure the event loop wakes up in
+ regular intervals and sends watchdog notification messages to the
+ service manager, if this was requested by the service
+ manager. Watchdog support is determined with
+ <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ and watchdog messages are sent with
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>. See
+ the <varname>WatchdogSec=</varname> setting in
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details on how to enable watchdog support for a service and
+ the protocol used. The wake-up interval is chosen as half the
+ watchdog timeout declared by the service manager via the
+ <varname>$WATCHDOG_USEC</varname> environment variable. If the
+ service manager did not request watchdog notifications, or if the
+ process was not invoked by the service manager this call with a
+ true <parameter>b</parameter> parameter executes no
+ operation. Passing a false <parameter>b</parameter> parameter will
+ disable the automatic sending of watchdog notification messages if
+ it was enabled before. Newly allocated event loop objects have
+ this feature disabled.</para>
+
+ <para>The first watchdog notification message is sent immediately
+ when <function>set_event_set_watchdog()</function> is invoked with
+ a true <parameter>b</parameter> parameter.</para>
+
+ <para>The watchdog logic is designed to allow the service manager
+ to automatically detect services that ceased processing of
+ incoming events, and thus appear "hung". Watchdog notifications
+ are sent out only at the beginning of each event loop
+ iteration. If an event source dispatch function blocks for an
+ excessively long time and does not return execution to the event
+ loop quickly, this might hence cause the notification message to
+ be delayed, and possibly result in abnormal program termination,
+ as configured in the service unit file.</para>
+
+ <para><function>sd_event_get_watchdog()</function> may be used to
+ determine whether watchdog support was previously requested by a
+ call to <function>sd_event_set_watchdog()</function> with a true
+ <parameter>b</parameter> parameter and successfully
+ enabled.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success, <function>sd_event_set_watchdog()</function> and
+ <function>sd_event_get_watchdog()</function> return a non-zero
+ positive integer if the service manager requested watchdog support
+ and watchdog support was successfully enabled. They return zero if
+ the service manager did not request watchdog support, or if
+ watchdog support was explicitly disabled with a false
+ <parameter>b</parameter> parameter. 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>-ECHILD</constant></term>
+
+ <listitem><para>The event loop has been created in a different process.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>The passed event loop object was invalid.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
+ <xi:include href="libsystemd-pkgconfig.xml" />
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_new</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_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_post</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>
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