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Diffstat (limited to 'man/sd_event_add_child.xml')
| -rw-r--r-- | man/sd_event_add_child.xml | 132 |
1 files changed, 86 insertions, 46 deletions
diff --git a/man/sd_event_add_child.xml b/man/sd_event_add_child.xml index 77bec4e706..d4b180cf03 100644 --- a/man/sd_event_add_child.xml +++ b/man/sd_event_add_child.xml @@ -21,7 +21,7 @@ along with systemd; If not, see <http://www.gnu.org/licenses/>. --> -<refentry id="sd_event_add_child"> +<refentry id="sd_event_add_child" xmlns:xi="http://www.w3.org/2001/XInclude"> <refentryinfo> <title>sd_event_add_child</title> @@ -45,13 +45,23 @@ <refnamediv> <refname>sd_event_add_child</refname> <refname>sd_event_source_get_child_pid</refname> + <refname>sd_event_child_handler_t</refname> - <refpurpose>Add a child state change event source to an event loop</refpurpose> + <refpurpose>Add a child process state change event source to an event loop</refpurpose> </refnamediv> <refsynopsisdiv> <funcsynopsis> - <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> + <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> + + <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo> + + <funcprototype> + <funcdef>typedef int (*<function>sd_event_child_handler_t</function>)</funcdef> + <paramdef>sd_event_source *<parameter>s</parameter></paramdef> + <paramdef>const siginfo_t *<parameter>si</parameter></paramdef> + <paramdef>void *<parameter>userdata</parameter></paramdef> + </funcprototype> <funcprototype> <funcdef>int <function>sd_event_add_child</function></funcdef> @@ -64,13 +74,6 @@ </funcprototype> <funcprototype> - <funcdef>typedef int (*<function>sd_event_child_handler_t</function>)</funcdef> - <paramdef>sd_event_source *<parameter>s</parameter></paramdef> - <paramdef>const siginfo_t *<parameter>si</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> @@ -83,42 +86,75 @@ <title>Description</title> <para><function>sd_event_add_child()</function> adds a new child - state change event source to an event loop object. The event loop - is specified in <parameter>event</parameter>, the event source is - returned in the <parameter>source</parameter> parameter. The - <parameter>pid</parameter> parameter specifies 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>const - siginfo_t</structname> structure containing the information about - the 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 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 - being stopped by a signal), and <constant>WCONTINUED</constant> - (watch for the child being resumed by a signal). See - <citerefentry><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry> + 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. The handler is enabled - for a single event (<constant>SD_EVENT_ONESHOT</constant>), - but this may be - changed with + child process. The handler is enabled for a single event + (<constant>SD_EVENT_ONESHOT</constant>), but this may be changed + with <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If the handler function returns a negative error code, it will be - disabled after the invocation, even if - <constant>SD_EVENT_ON</constant> mode is set. + disabled after the invocation, even if the + <constant>SD_EVENT_ON</constant> mode was requested before. </para> + <para>To destroy an event source object use + <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + but note that the event source is only removed from the event loop + when all references to the event source are dropped. To make sure + an event source does not fire anymore, even when there's still a + reference to it kept, consider setting the event source to + <constant>SD_EVENT_OFF</constant> with + <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> + + <para>If the 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 + event source is considered "floating", and will be destroyed + implicitly when the event loop itself is destroyed.</para> + + <para>Note that the <parameter>handler</parameter> function is + invoked at a time where the child process is not reaped yet (and + thus still is exposed as a zombie process by the kernel). However, + the child will be reaped automatically after the function + returns. Child processes for which no child process state change + event sources are installed will not be reaped by the event loop + implementation.</para> + + <para>If both a child process state change event source and a + <constant>SIGCHLD</constant> signal event source is installed in + the same event loop, the configured event source priorities decide + which event source is dispatched first. If the signal handler is + processed first, it should leave the child processes for which + child process state change event sources are installed unreaped.</para> + <para><function>sd_event_source_get_child_pid()</function> - retrieves the configured <parameter>pid</parameter> of a child - state change event source created previously with + retrieves the configured PID of a child process state change event + source created previously with <function>sd_event_add_child()</function>. It takes the event source object as the <parameter>source</parameter> parameter and a - pointer to <type>pid_t</type> to return the result in. + pointer to a <type>pid_t</type> variable to return the process ID + in. </para> </refsect1> @@ -158,7 +194,7 @@ <term><constant>-EBUSY</constant></term> <listitem><para>A handler is already installed for this - child.</para></listitem> + child process.</para></listitem> </varlistentry> @@ -176,19 +212,17 @@ </varlistentry> - </variablelist> - </refsect1> + <varlistentry> + <term><constant>-EDOM</constant></term> - <refsect1> - <title>Notes</title> + <listitem><para>The passed event source is not a child process event source.</para></listitem> + </varlistentry> - <para><function>sd_event_add_child()</function> and the other functions - described here 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> + </variablelist> </refsect1> + <xi:include href="libsystemd-pkgconfig.xml" /> + <refsect1> <title>See Also</title> @@ -196,10 +230,16 @@ <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_now</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_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, - <citerefentry><refentrytitle>sd_event_source_set_enabled</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> </para> </refsect1> |