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Diffstat (limited to 'src/libsystemd/sd_event_set_watchdog.xml')
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1 files changed, 177 insertions, 0 deletions
diff --git a/src/libsystemd/sd_event_set_watchdog.xml b/src/libsystemd/sd_event_set_watchdog.xml new file mode 100644 index 0000000000..cbc5bc0836 --- /dev/null +++ b/src/libsystemd/sd_event_set_watchdog.xml @@ -0,0 +1,177 @@ +<?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> |