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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.
167 lines
6.9 KiB
XML
167 lines
6.9 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 2015 Lennart Poettering
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-->
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<refentry id="sd_event_set_watchdog" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_event_set_watchdog</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</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_set_watchdog</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_set_watchdog</refname>
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<refname>sd_event_get_watchdog</refname>
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<refpurpose>Enable event loop watchdog support</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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<funcprototype>
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<funcdef>int <function>sd_event_set_watchdog</function></funcdef>
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<paramdef>sd_event *<parameter>event</parameter></paramdef>
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<paramdef>int b</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_get_watchdog</function></funcdef>
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<paramdef>sd_event *<parameter>event</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><function>sd_event_set_watchdog()</function> may be used to
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enable or disable automatic watchdog notification support in the
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event loop object specified in the <parameter>event</parameter>
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parameter. Specifically, depending on the <parameter>b</parameter>
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boolean argument this will make sure the event loop wakes up in
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regular intervals and sends watchdog notification messages to the
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service manager, if this was requested by the service
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manager. Watchdog support is determined with
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<citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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and watchdog messages are sent with
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<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>. See
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the <varname>WatchdogSec=</varname> setting in
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details on how to enable watchdog support for a service and
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the protocol used. The wake-up interval is chosen as half the
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watchdog timeout declared by the service manager via the
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<varname>$WATCHDOG_USEC</varname> environment variable. If the
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service manager did not request watchdog notifications, or if the
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process was not invoked by the service manager this call with a
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true <parameter>b</parameter> parameter executes no
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operation. Passing a false <parameter>b</parameter> parameter will
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disable the automatic sending of watchdog notification messages if
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it was enabled before. Newly allocated event loop objects have
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this feature disabled.</para>
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<para>The first watchdog notification message is sent immediately
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when <function>set_event_set_watchdog()</function> is invoked with
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a true <parameter>b</parameter> parameter.</para>
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<para>The watchdog logic is designed to allow the service manager
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to automatically detect services that ceased processing of
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incoming events, and thus appear "hung". Watchdog notifications
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are sent out only at the beginning of each event loop
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iteration. If an event source dispatch function blocks for an
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excessively long time and does not return execution to the event
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loop quickly, this might hence cause the notification message to
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be delayed, and possibly result in abnormal program termination,
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as configured in the service unit file.</para>
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<para><function>sd_event_get_watchdog()</function> may be used to
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determine whether watchdog support was previously requested by a
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call to <function>sd_event_set_watchdog()</function> with a true
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<parameter>b</parameter> parameter and successfully
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enabled.</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, <function>sd_event_set_watchdog()</function> and
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<function>sd_event_get_watchdog()</function> return a non-zero
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positive integer if the service manager requested watchdog support
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and watchdog support was successfully enabled. They return zero if
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the service manager did not request watchdog support, or if
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watchdog support was explicitly disabled with a false
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<parameter>b</parameter> parameter. On failure, they return a
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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>-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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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>The passed event loop object was invalid.</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_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_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_post</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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