-<?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">
-
-<!--
- SPDX-License-Identifier: LGPL-2.1+
-
- This file is part of systemd.
-
- Copyright 2014 Zbigniew Jędrzejewski-Szmek
-
- 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.
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- 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.
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- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="sd_event_add_child" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_event_add_child</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>More text</contrib>
- <firstname>Zbigniew</firstname>
- <surname>Jędrzejewski-Szmek</surname>
- <email>zbyszek@in.waw.pl</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
<refnamediv>
<refname>sd_event_add_child</refname>
+ <refname>sd_event_add_child_pidfd</refname>
<refname>sd_event_source_get_child_pid</refname>
+ <refname>sd_event_source_get_child_pidfd</refname>
+ <refname>sd_event_source_get_child_pidfd_own</refname>
+ <refname>sd_event_source_set_child_pidfd_own</refname>
+ <refname>sd_event_source_get_child_process_own</refname>
+ <refname>sd_event_source_set_child_process_own</refname>
+ <refname>sd_event_source_send_child_signal</refname>
<refname>sd_event_child_handler_t</refname>
<refpurpose>Add a child process state change event source to an event loop</refpurpose>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
+ <funcprototype>
+ <funcdef>int <function>sd_event_add_child_pidfd</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+ <paramdef>int <parameter>pidfd</parameter></paramdef>
+ <paramdef>int <parameter>options</parameter></paramdef>
+ <paramdef>sd_event_child_handler_t <parameter>handler</parameter></paramdef>
+ <paramdef>void *<parameter>userdata</parameter></paramdef>
+ </funcprototype>
+
<funcprototype>
<funcdef>int <function>sd_event_source_get_child_pid</function></funcdef>
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
<paramdef>pid_t *<parameter>pid</parameter></paramdef>
</funcprototype>
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_child_pidfd</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_child_pidfd_own</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_set_child_pidfd_own</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>int <parameter>own</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_child_process_own</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_set_child_process_own</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>int <parameter>own</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_send_child_signal</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>int <parameter>sig</parameter></paramdef>
+ <paramdef>const siginfo_t *<parameter>info</parameter></paramdef>
+ <paramdef>unsigned <parameter>flags</parameter></paramdef>
+ </funcprototype>
+
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
- <para><function>sd_event_add_child()</function> adds a new child
- process state change event source to an event loop. The event loop
- object is specified in the <parameter>event</parameter> parameter,
- the event source object is returned in the
- <parameter>source</parameter> parameter. The
- <parameter>pid</parameter> parameter specifies the PID of the
- process to watch. The <parameter>handler</parameter> must
- reference a function to call when the process changes state. The
- handler function will be passed the
- <parameter>userdata</parameter> pointer, which may be chosen
- freely by the caller. The handler also receives a pointer to a
- <structname>siginfo_t</structname> structure containing
- information about the child process event. The
- <parameter>options</parameter> parameter determines which state
- changes will be watched for. It must contain an OR-ed mask of
- <constant>WEXITED</constant> (watch for the child process
- terminating), <constant>WSTOPPED</constant> (watch for the child
- process being stopped by a signal), and
- <constant>WCONTINUED</constant> (watch for the child process being
- resumed by a signal). See <citerefentry
- project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
- for further information.</para>
+ <para><function>sd_event_add_child()</function> adds a new child process state change event source to an
+ event loop. The event loop object is specified in the <parameter>event</parameter> parameter, the event
+ source object is returned in the <parameter>source</parameter> parameter. The <parameter>pid</parameter>
+ parameter specifies the PID of the process to watch, which must be a direct child process of the invoking
+ process. The <parameter>handler</parameter> must reference a function to call when the process changes
+ state. The handler function will be passed the <parameter>userdata</parameter> pointer, which may be
+ chosen freely by the caller. The handler also receives a pointer to a <structname>siginfo_t</structname>
+ structure containing information about the child process event. The <parameter>options</parameter>
+ parameter determines which state changes will be watched for. It must contain an OR-ed mask of
+ <constant>WEXITED</constant> (watch for the child process terminating), <constant>WSTOPPED</constant>
+ (watch for the child process being stopped by a signal), and <constant>WCONTINUED</constant> (watch for
+ the child process being resumed by a signal). See <citerefentry
+ project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry> for
+ further information.</para>
<para>Only a single handler may be installed for a specific
child process. The handler is enabled for a single event
<constant>SD_EVENT_OFF</constant> with
<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+ <para>The <constant>SIGCHLD</constant> signal must be blocked in all threads before this function is
+ called (using <citerefentry
+ project='man-pages'><refentrytitle>sigprocmask</refentrytitle><manvolnum>2</manvolnum></citerefentry> or
+ <citerefentry
+ project='man-pages'><refentrytitle>pthread_sigmask</refentrytitle><manvolnum>3</manvolnum></citerefentry>).</para>
+
<para>If the second parameter of
<function>sd_event_add_child()</function> is passed as NULL no
reference to the event source object is returned. In this case the
processed first, it should leave the child processes for which
child process state change event sources are installed unreaped.</para>
+ <para><function>sd_event_add_child_pidfd()</function> is similar to
+ <function>sd_event_add_child()</function> but takes a file descriptor referencing the process ("pidfd")
+ instead of the numeric PID. A suitable file descriptor may be acquired via <citerefentry
+ project='man-pages'><refentrytitle>pidfd_open</refentrytitle><manvolnum>2</manvolnum></citerefentry> and
+ related calls. The passed file descriptor is not closed when the event source is freed again, unless
+ <function>sd_event_source_set_child_pidfd_own()</function> is used to turn this behaviour on. Note that
+ regardless which of <function>sd_event_add_child()</function> and
+ <function>sd_event_add_child_pidfd()</function> is used for allocating an event source, the watched
+ process has to be a direct child process of the invoking process. Also in both cases
+ <constant>SIGCHLD</constant> has to be blocked in the invoking process.</para>
+
<para><function>sd_event_source_get_child_pid()</function>
retrieves the configured PID of a child process state change event
source created previously with
pointer to a <type>pid_t</type> variable to return the process ID
in.
</para>
+
+ <para><function>sd_event_source_get_child_pidfd()</function> retrieves the file descriptor referencing
+ the watched process ("pidfd") if this functionality is available. On kernels that support the concept the
+ event loop will make use of pidfds to watch child processes, regardless if the individual event sources
+ are allocated via <function>sd_event_add_child()</function> or
+ <function>sd_event_add_child_pidfd()</function>. If the latter call was used to allocate the event
+ source, this function returns the file descriptor used for allocation. On kernels that do not support the
+ pidfd concept this function will fail with <constant>EOPNOTSUPP</constant>. This call takes the event
+ source object as the <parameter>source</parameter> parameter and returns the numeric file descriptor.
+ </para>
+
+ <para><function>sd_event_source_get_child_pidfd_own()</function> may be used to query whether the pidfd
+ the event source encapsulates shall be closed when the event source is freed. This function returns zero
+ if the pidfd shall be left open, and positive if it shall be closed automatically. By default this
+ setting defaults to on if the event source was allocated via <function>sd_event_add_child()</function>
+ and off if it was allocated via <function>sd_event_add_child_pidfd()</function>. The
+ <function>sd_event_source_set_child_pidfd_own()</function> function may be used to change the setting and
+ takes a boolean parameter with the new setting.</para>
+
+ <para><function>sd_event_source_get_child_process_own()</function> may be used to query whether the
+ process the event source watches shall be killed (with <constant>SIGKILL</constant>) and reaped when the
+ event source is freed. This function returns zero if the process shell be left running, and positive if
+ it shall be killed and reaped automatically. By default this setting defaults to off. The
+ <function>sd_event_source_set_child_process_own()</function> function may be used to change the setting
+ and takes a boolean parameter with the new setting. Note that currently if the calling process is
+ terminated abnormally the watched process might survive even thought the event source ceases to
+ exist. This behaviour might change eventually.</para>
+
+ <para><function>sd_event_source_send_child_signal()</function> may be used to send a UNIX signal to the
+ watched process. If the pidfd concept is supported in the kernel, this is implemented via <citerefentry
+ project='man-pages'><refentrytitle>pidfd_send_signal</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ and otherwise via <citerefentry
+ project='man-pages'><refentrytitle>rt_sigqueueinfo</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ (or via <citerefentry
+ project='man-pages'><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry> in case
+ <parameter>info</parameter> is <constant>NULL</constant>). The specified parameters match those of these
+ underlying system calls, except that the <parameter>info</parameter> is never modified (and is thus
+ declared constant). Like for the underlying system calls, the <parameter>flags</parameter> parameter
+ currently must be zero.</para>
</refsect1>
<refsect1>
<para>On success, these functions return 0 or a positive
integer. On failure, they return a negative errno-style error
code.</para>
- </refsect1>
- <refsect1>
- <title>Errors</title>
+ <refsect2>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-ENOMEM</constant></term>
- <para>Returned errors may indicate the following problems:</para>
+ <listitem><para>Not enough memory to allocate an object.</para></listitem>
+ </varlistentry>
- <variablelist>
- <varlistentry>
- <term><constant>-ENOMEM</constant></term>
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
- <listitem><para>Not enough memory to allocate an object.</para></listitem>
- </varlistentry>
+ <listitem><para>An invalid argument has been passed. This includes
+ specifying an empty mask in <parameter>options</parameter> or a mask
+ which contains values different than a combination of
+ <constant>WEXITED</constant>, <constant>WSTOPPED</constant>, and
+ <constant>WCONTINUED</constant>.
+ </para></listitem>
- <varlistentry>
- <term><constant>-EINVAL</constant></term>
+ </varlistentry>
- <listitem><para>An invalid argument has been passed. This includes
- specifying an empty mask in <parameter>options</parameter> or a mask
- which contains values different than a combination of
- <constant>WEXITED</constant>, <constant>WSTOPPED</constant>, and
- <constant>WCONTINUED</constant>.
- </para></listitem>
+ <varlistentry>
+ <term><constant>-EBUSY</constant></term>
- </varlistentry>
+ <listitem><para>A handler is already installed for this child process, or
+ <constant>SIGCHLD</constant> is not blocked.</para></listitem>
- <varlistentry>
- <term><constant>-EBUSY</constant></term>
+ </varlistentry>
- <listitem><para>A handler is already installed for this
- child process.</para></listitem>
+ <varlistentry>
+ <term><constant>-ESTALE</constant></term>
- </varlistentry>
+ <listitem><para>The event loop is already terminated.</para></listitem>
- <varlistentry>
- <term><constant>-ESTALE</constant></term>
+ </varlistentry>
- <listitem><para>The event loop is already terminated.</para></listitem>
+ <varlistentry>
+ <term><constant>-ECHILD</constant></term>
- </varlistentry>
+ <listitem><para>The event loop has been created in a different process.</para></listitem>
- <varlistentry>
- <term><constant>-ECHILD</constant></term>
+ </varlistentry>
- <listitem><para>The event loop has been created in a different process.</para></listitem>
+ <varlistentry>
+ <term><constant>-EDOM</constant></term>
- </varlistentry>
+ <listitem><para>The passed event source is not a child process event source.</para></listitem>
+ </varlistentry>
- <varlistentry>
- <term><constant>-EDOM</constant></term>
+ <varlistentry>
+ <term><constant>-EOPNOTSUPP</constant></term>
- <listitem><para>The passed event source is not a child process event source.</para></listitem>
- </varlistentry>
+ <listitem><para>A pidfd was requested but the kernel does not support this concept.</para></listitem>
+ </varlistentry>
- </variablelist>
+ </variablelist>
+ </refsect2>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<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_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>sd_event_source_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>sigprocmask</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>pthread_sigmask</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>pidfd_open</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>pidfd_send_signal</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>rt_sigqueueinfo</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry>
</para>
</refsect1>
projects / thirdparty / systemd.git / blobdiff