mirror of
https://github.com/systemd/systemd.git
synced 2024-12-26 03:22:00 +03:00
9809a788e4
The meaning of the return value, the default handlers, and loop exiting are now described.
327 lines
17 KiB
XML
327 lines
17 KiB
XML
<?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-or-later -->
|
|
|
|
<refentry id="sd_event_add_time" xmlns:xi="http://www.w3.org/2001/XInclude">
|
|
|
|
<refentryinfo>
|
|
<title>sd_event_add_time</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>sd_event_add_time</refentrytitle>
|
|
<manvolnum>3</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>sd_event_add_time</refname>
|
|
<refname>sd_event_add_time_relative</refname>
|
|
<refname>sd_event_source_get_time</refname>
|
|
<refname>sd_event_source_set_time</refname>
|
|
<refname>sd_event_source_set_time_relative</refname>
|
|
<refname>sd_event_source_get_time_accuracy</refname>
|
|
<refname>sd_event_source_set_time_accuracy</refname>
|
|
<refname>sd_event_source_get_time_clock</refname>
|
|
<refname>sd_event_time_handler_t</refname>
|
|
|
|
<refpurpose>Add a timer event source to an event loop</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<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_time_handler_t</function>)</funcdef>
|
|
<paramdef>sd_event_source *<parameter>s</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_event_add_time</function></funcdef>
|
|
<paramdef>sd_event *<parameter>event</parameter></paramdef>
|
|
<paramdef>sd_event_source **<parameter>source</parameter></paramdef>
|
|
<paramdef>clockid_t <parameter>clock</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>accuracy</parameter></paramdef>
|
|
<paramdef>sd_event_time_handler_t <parameter>handler</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_event_add_time_relative</function></funcdef>
|
|
<paramdef>sd_event *<parameter>event</parameter></paramdef>
|
|
<paramdef>sd_event_source **<parameter>source</parameter></paramdef>
|
|
<paramdef>clockid_t <parameter>clock</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>accuracy</parameter></paramdef>
|
|
<paramdef>sd_event_time_handler_t <parameter>handler</parameter></paramdef>
|
|
<paramdef>void *<parameter>userdata</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_event_source_get_time</function></funcdef>
|
|
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
|
<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_event_source_set_time</function></funcdef>
|
|
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_event_source_set_time_relative</function></funcdef>
|
|
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_event_source_get_time_accuracy</function></funcdef>
|
|
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
|
<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_event_source_set_time_accuracy</function></funcdef>
|
|
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_event_source_get_time_clock</function></funcdef>
|
|
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
|
|
<paramdef>clockid_t *<parameter>clock</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para><function>sd_event_add_time()</function> adds a new timer 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>clock</parameter> parameter takes a clock identifier, one
|
|
of <constant>CLOCK_REALTIME</constant>, <constant>CLOCK_MONOTONIC</constant>, <constant>CLOCK_BOOTTIME</constant>,
|
|
<constant>CLOCK_REALTIME_ALARM</constant>, or <constant>CLOCK_BOOTTIME_ALARM</constant>. See
|
|
<citerefentry><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry> for details
|
|
regarding the various types of clocks. The <parameter>usec</parameter> parameter specifies the earliest time, in
|
|
microseconds (µs), relative to the clock's epoch, when the timer shall be triggered. If a time already in the past
|
|
is specified (including <constant>0</constant>), this timer source "fires" immediately and is ready to be
|
|
dispatched. If the parameter is specified as <constant>UINT64_MAX</constant> the timer event will never elapse,
|
|
which may be used as an alternative to explicitly disabling a timer event source with
|
|
<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
|
|
<parameter>accuracy</parameter> parameter specifies an additional accuracy value in µs specifying how much the
|
|
timer event may be delayed. Use <constant>0</constant> to select the default accuracy (250ms). Use 1µs for maximum
|
|
accuracy. Consider specifying 60000000µs (1min) or larger for long-running events that may be delayed
|
|
substantially. Picking higher accuracy values allows the system to coalesce timer events more aggressively,
|
|
improving power efficiency.</para>
|
|
|
|
<para>The <parameter>handler</parameter> is a function to call when the timer elapses or
|
|
<constant>NULL</constant>. The <parameter>userdata</parameter> pointer will be passed to the handler
|
|
function, and may be chosen freely by the caller. The configured trigger time is also passed to the
|
|
handler, even if the call actually happens slightly later, subject to the specified accuracy value, the
|
|
kernel timer slack (see
|
|
<citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>), and
|
|
additional scheduling latencies. To query the actual time the handler was called use
|
|
<citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
|
|
handler may return negative to signal an error (see below), other return values are ignored. If
|
|
<parameter>handler</parameter> is <constant>NULL</constant>, a default handler that calls
|
|
<citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry> will be
|
|
used.</para>
|
|
|
|
<para>By default, the timer will elapse once (<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 either be disabled after the invocation,
|
|
even if the <constant>SD_EVENT_ON</constant> mode was requested before, or it will cause the loop to
|
|
terminate, see
|
|
<citerefentry><refentrytitle>sd_event_source_set_exit_on_failure</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
Note that a timer event set to <constant>SD_EVENT_ON</constant> will fire continuously unless its
|
|
configured time is updated using <function>sd_event_source_set_time()</function>.</para>
|
|
|
|
<para><function>sd_event_add_time_relative()</function> is like <function>sd_event_add_time()</function>,
|
|
but takes a relative time specification. It's relative to the current time of the event loop iteration,
|
|
as returned by
|
|
<citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</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 if it is still referenced,
|
|
disable the event source using
|
|
<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
with <constant>SD_EVENT_OFF</constant>.</para>
|
|
|
|
<para>If the second parameter of
|
|
<function>sd_event_add_time()</function> is
|
|
<constant>NULL</constant> 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>If the <parameter>handler</parameter> parameter to <function>sd_event_add_time()</function> is
|
|
<constant>NULL</constant>, and the event source fires, this will be considered a request to exit the
|
|
event loop. In this case, the <parameter>userdata</parameter> parameter, cast to an integer, is passed as
|
|
the exit code parameter to
|
|
<citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
|
|
|
|
<para>Use <constant>CLOCK_BOOTTIME_ALARM</constant> and
|
|
<constant>CLOCK_REALTIME_ALARM</constant> to define event sources
|
|
that may wake up the system from suspend.</para>
|
|
|
|
<para>In order to set up relative timers (that is, relative to the
|
|
current time), retrieve the current time via
|
|
<citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
add the desired timespan to it, and use the result as
|
|
the <parameter>usec</parameter> parameter to
|
|
<function>sd_event_add_time()</function>.</para>
|
|
|
|
<para>In order to set up repetitive timers (that is, timers that
|
|
are triggered in regular intervals), set up the timer normally,
|
|
for the first invocation. Each time the event handler is invoked,
|
|
update the timer's trigger time with
|
|
<citerefentry><refentrytitle>sd_event_source_set_time</refentrytitle><manvolnum>3</manvolnum></citerefentry> for the next timer
|
|
iteration, and reenable the timer using
|
|
<function>sd_event_source_set_enabled()</function>. To calculate
|
|
the next point in time to pass to
|
|
<function>sd_event_source_set_time()</function>, either use as
|
|
base the <parameter>usec</parameter> parameter passed to the timer
|
|
callback, or the timestamp returned by
|
|
<function>sd_event_now()</function>. In the former case timer
|
|
events will be regular, while in the latter case the scheduling
|
|
latency will keep accumulating on the timer.</para>
|
|
|
|
<para><function>sd_event_source_get_time()</function> retrieves the configured time value of an event
|
|
source created previously with <function>sd_event_add_time()</function> or
|
|
<function>sd_event_add_time_relative()</function>. It takes the event source object and a pointer to a
|
|
variable to store the time in, relative to the selected clock's epoch, in µs. The returned value is
|
|
relative to the epoch, even if the event source was created with a relative time via
|
|
<function>sd_event_add_time_relative()</function>.</para>
|
|
|
|
<para><function>sd_event_source_set_time()</function> changes the time of an event source created
|
|
previously with <function>sd_event_add_time()</function> or
|
|
<function>sd_event_add_time_relative()</function>. It takes the event source object and a time relative
|
|
to the selected clock's epoch, in µs.</para>
|
|
|
|
<para><function>sd_event_source_set_time_relative()</function> is similar to
|
|
<function>sd_event_source_set_time()</function>, but takes a time relative to the current time of the
|
|
event loop iteration, as returned by <function>sd_event_now()</function>.</para>
|
|
|
|
<para><function>sd_event_source_get_time_accuracy()</function>
|
|
retrieves the configured accuracy value of an event source
|
|
created previously with <function>sd_event_add_time()</function>. It
|
|
takes the event source object and a pointer to a variable to store
|
|
the accuracy in. The accuracy is specified in µs.</para>
|
|
|
|
<para><function>sd_event_source_set_time_accuracy()</function>
|
|
changes the configured accuracy of a timer event source created
|
|
previously with <function>sd_event_add_time()</function>. It takes
|
|
the event source object and accuracy, in µs.</para>
|
|
|
|
<para><function>sd_event_source_get_time_clock()</function>
|
|
retrieves the configured clock of an event source created
|
|
previously with <function>sd_event_add_time()</function>. It takes
|
|
the event source object and a pointer to a variable to store the
|
|
clock identifier in.</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>
|
|
|
|
<refsect2>
|
|
<title>Errors</title>
|
|
|
|
<para>Returned values may indicate the following problems:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><constant>-ENOMEM</constant></term>
|
|
|
|
<listitem><para>Not enough memory to allocate an object.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-EINVAL</constant></term>
|
|
|
|
<listitem><para>An invalid argument has been passed.</para></listitem>
|
|
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ESTALE</constant></term>
|
|
|
|
<listitem><para>The event loop is already terminated.</para></listitem>
|
|
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-ECHILD</constant></term>
|
|
|
|
<listitem><para>The event loop has been created in a different process.</para></listitem>
|
|
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-EOPNOTSUPP</constant></term>
|
|
|
|
<listitem><para>The selected clock is not supported by the event loop implementation.</para></listitem>
|
|
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-EDOM</constant></term>
|
|
|
|
<listitem><para>The passed event source is not a timer event source.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><constant>-EOVERFLOW</constant></term>
|
|
|
|
<listitem><para>The passed relative time is outside of the allowed range for time values (i.e. the
|
|
specified value added to the current time is outside the 64 bit unsigned integer range).</para></listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
</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_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_event_add_io</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_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><refentrytitle>sd_event_source_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
|
|
<citerefentry project='man-pages'><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
|
|
<citerefentry project='man-pages'><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|