Merge pull request #1964 from poettering/sd-event-man

Finish the documentation for sd-event.h

1 files changed, 177 insertions, 0 deletions

diff --git a/man/sd_event_set_watchdog.xml b/man/sd_event_set_watchdog.xml
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+<?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 &lt;systemd/sd-event.h&gt;</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>