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author | Lennart Poettering <lennart@poettering.net> | 2018-05-30 16:33:12 +0200 |
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committer | Lennart Poettering <lennart@poettering.net> | 2018-05-30 17:34:34 +0200 |
commit | 1004b2c7bc5adb8dba23e209c88f74a02ac5f709 (patch) | |
tree | d9110c324dfafc187265464309da9767b5d7859b /man | |
parent | 303acb7f2db3240491abb3cd8bdba90ecfc9306d (diff) | |
download | systemd-1004b2c7bc5adb8dba23e209c88f74a02ac5f709.tar.gz |
man: document the new sd_bus_slot_set_floating() call
Also extend the memory management description of sd-bus highlighting the
effect of "floating" slot objects a bit.
Diffstat (limited to 'man')
-rw-r--r-- | man/rules/meson.build | 1 | ||||
-rw-r--r-- | man/sd_bus_add_match.xml | 7 | ||||
-rw-r--r-- | man/sd_bus_default.xml | 35 | ||||
-rw-r--r-- | man/sd_bus_slot_set_floating.xml | 118 |
4 files changed, 144 insertions, 17 deletions
diff --git a/man/rules/meson.build b/man/rules/meson.build index d3ed9f8a6a..0fb7978c21 100644 --- a/man/rules/meson.build +++ b/man/rules/meson.build @@ -231,6 +231,7 @@ manpages = [ ['sd_bus_set_connected_signal', '3', ['sd_bus_get_connected_signal'], ''], ['sd_bus_set_sender', '3', ['sd_bus_get_sender'], ''], ['sd_bus_set_watch_bind', '3', ['sd_bus_get_watch_bind'], ''], + ['sd_bus_slot_set_floating', '3', ['sd_bus_slot_get_floating'], ''], ['sd_bus_track_add_name', '3', ['sd_bus_track_add_sender', diff --git a/man/sd_bus_add_match.xml b/man/sd_bus_add_match.xml index 07a7b0ea17..13f2b06af0 100644 --- a/man/sd_bus_add_match.xml +++ b/man/sd_bus_add_match.xml @@ -132,7 +132,9 @@ at a later time with <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If specified as <constant>NULL</constant> the lifetime of the match is bound to the lifetime of the bus object itself, and the - match cannot be removed independently.</para> + match is generally not removed independently. See + <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry> for + details.</para> <para>The message <parameter>m</parameter> passed to the callback is only borrowed, that is, the callback should not call <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> @@ -175,7 +177,8 @@ <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, - <citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry> + <citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry> </para> </refsect1> diff --git a/man/sd_bus_default.xml b/man/sd_bus_default.xml index f36272e854..da06fb9cbf 100644 --- a/man/sd_bus_default.xml +++ b/man/sd_bus_default.xml @@ -206,21 +206,26 @@ <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to drop the reference.</para> - <para>Queued but unwritten/unread messages also keep a reference - to their bus connection object. For this reason, even if an - application dropped all references to a bus connection, it might - not get destroyed right away. Until all incoming queued - messages are read, and until all outgoing unwritten messages are - written, the bus object will stay - alive. <function>sd_bus_flush()</function> may be used to write - all outgoing queued messages so they drop their references. To - flush the unread incoming messages, use - <function>sd_bus_close()</function>, which will also close the bus - connection. When using the default bus logic, it is a good idea to - first invoke <function>sd_bus_flush()</function> followed by - <function>sd_bus_close()</function> when a thread or process - terminates, and thus its bus connection object should be - freed.</para> + <para>Queued but unwritten/unread messages keep a reference to their bus connection object. For this reason, even + if an application dropped all references to a bus connection, it might not get destroyed right away. Until all + incoming queued messages are read, and until all outgoing unwritten messages are written, the bus object will stay + alive. <function>sd_bus_flush()</function> may be used to write all outgoing queued messages so they drop their + references. To flush the unread incoming messages, use <function>sd_bus_close()</function>, which will also close + the bus connection. When using the default bus logic, it is a good idea to first invoke + <function>sd_bus_flush()</function> followed by <function>sd_bus_close()</function> when a thread or process + terminates, and thus its bus connection object should be freed.</para> + + <para>Normally, slot objects (as created by + <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> and similar + calls) keep a reference to their bus connection object, too. Thus, as long as a bus slot object remains referenced + its bus object will remain allocated too. Optionally, bus slot objects may be placed in "floating" mode. When in + floating mode the life cycle of the bus slot object is bound to the bus object, i.e. when the bus object is freed + the bus slot object is automatically unreferenced too. The floating state of a slot object may be controlled + explicitly with + <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + though usually floating bus slot objects are created by passing <constant>NULL</constant> as the + <parameter>slot</parameter> parameter of <function>sd_bus_add_match()</function> and related calls, thus indicating + that the caller is not directly interested in referencing and managing the bus slot object.</para> <para>The life cycle of the default bus connection should be the responsibility of the code that creates/owns the thread the diff --git a/man/sd_bus_slot_set_floating.xml b/man/sd_bus_slot_set_floating.xml new file mode 100644 index 0000000000..2ac5090193 --- /dev/null +++ b/man/sd_bus_slot_set_floating.xml @@ -0,0 +1,118 @@ +<?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+ --> + +<refentry id="sd_bus_slot_set_floating"> + + <refentryinfo> + <title>sd_bus_slot_set_floating</title> + <productname>systemd</productname> + </refentryinfo> + + <refmeta> + <refentrytitle>sd_bus_slot_set_floating</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + + <refnamediv> + <refname>sd_bus_slot_set_floating</refname> + <refname>sd_bus_slot_get_floating</refname> + + <refpurpose>Control whether a bus slot object is "floating".</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> + + <funcprototype> + <funcdef>int <function>sd_bus_slot_set_floating</function></funcdef> + <paramdef>sd_bus_slot *<parameter>bus</parameter></paramdef> + <paramdef>int <parameter>b</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_bus_slot_get_floating</function></funcdef> + <paramdef>sd_bus_slot *<parameter>slot</parameter></paramdef> + </funcprototype> + + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><function>sd_bus_slot_set_floating()</function> controls whether the specified bus slot object + <parameter>slot</parameter> shall be "floating" or not. A floating bus slot object's lifetime is bound to the + lifetime of the bus object it is associated with, meaning that it remains allocated as long as the bus object + itself and is freed automatically when the bus object is freed. Regular (i.e. non-floating) bus slot objects keep + the bus referenced, hence the bus object remains allocated at least as long as there remains at least one + referenced bus slot object around. The floating state hence controls the direction of referencing between the bus + object and the bus slot objects: if floating the bus pins the the bus slot, and otherwise the bus slot pins the bus + objects. Use <function>sd_bus_slot_set_floating()</function> to switch between both modes: if the + <parameter>b</parameter> parameter is zero, the slot object is considered floating, otherwise it is made a regular + (non-floating) slot object.</para> + + <para>Bus slot objects may be allocated with calls such as + <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If the + <parameter>slot</parameter> of these functions is non-<constant>NULL</constant> the slot object will be of the + regular kind (i.e. non-floating), otherwise it will be created floating. With + <function>sd_bus_slot_set_floating()</function> a bus slot object allocated as regular can be converted into a + floating object and back. This is particularly useful for creating a bus slot object, then changing parameters of + it, and then turning it into a floating object, whose lifecycle is managed by the bus object.</para> + + <para><function>sd_bus_slot_get_floating()</function> returns the current floating state of the specified bus slot + object. It returns negative on error, zero if the bus slot object is a regular (non-floating) object and positive + otherwise.</para> + </refsect1> + + <refsect1> + <title>Return Value</title> + + <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> + + <para>Returned errors may indicate the following problems:</para> + + <variablelist> + <varlistentry> + <term><constant>-ECHILD</constant></term> + + <listitem><para>The bus connection has been created in a different process.</para></listitem> + </varlistentry> + + <varlistentry> + <term><constant>-ESTALE</constant></term> + + <listitem><para>The bus object the specified bus slot object is associated with has already been freed, and + hence no change in the floating state can be made anymore.</para></listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Notes</title> + + <para><function>sd_bus_slot_set_floating()</function> and <function>sd_bus_slot_get_floating()</function> are + available as a shared library, which can be compiled and linked to with the + <constant>libsystemd</constant> <citerefentry + project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> + </refsect1> + + <refsect1> + <title>See Also</title> + + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |