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sd-event objects use hashmaps, which use module-global state, so it is not safe to pass a sd-event object created by a module instance to another module instance (e.g.: when two libraries static linking sd-event are pulled in a single process). Initialize a random per-module origin id and store it in the object, and compare it when entering a public API, and error out if they don't match, together with the PID.
115 lines
4.3 KiB
XML
115 lines
4.3 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_event_now" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_event_now</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_event_now</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_event_now</refname>
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<refpurpose>Retrieve current event loop iteration timestamp</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_event_now</function></funcdef>
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<paramdef>sd_event *<parameter>event</parameter></paramdef>
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<paramdef>clockid_t <parameter>clock</parameter></paramdef>
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<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_event_now()</function> returns the time when
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the most recent event loop iteration began. A timestamp
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is taken right after returning from the event sleep, and before
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dispatching any event sources. The <parameter>event</parameter>
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parameter specifies the event loop object to retrieve the timestamp
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from. The <parameter>clock</parameter> parameter specifies the clock to
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retrieve the timestamp for, and is one of
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<constant>CLOCK_REALTIME</constant> (or equivalently
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<constant>CLOCK_REALTIME_ALARM</constant>),
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<constant>CLOCK_MONOTONIC</constant>, or
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<constant>CLOCK_BOOTTIME</constant> (or equivalently
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<constant>CLOCK_BOOTTIME_ALARM</constant>), see
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<citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for more information on the various clocks. The retrieved
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timestamp is stored in the <parameter>usec</parameter> parameter,
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in µs since the clock's epoch. If this function is invoked before
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the first event loop iteration, the current time is returned, as
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reported by <function>clock_gettime()</function>. To distinguish
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this case from a regular invocation the return value will be
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positive, and zero when the returned timestamp refers to an actual
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event loop iteration.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>If the first event loop iteration has not run yet <function>sd_event_now()</function> writes
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current time to <parameter>usec</parameter> and returns a positive return value. Otherwise, it will
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write the requested timestamp to <parameter>usec</parameter> and return 0. On failure, the call returns a
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negative errno-style error code.</para>
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<refsect2>
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<title>Errors</title>
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<para>Returned values may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>An invalid parameter was passed.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EOPNOTSUPP</constant></term>
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<listitem><para>Unsupported clock type.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The event loop object was created in a different process, library or module instance.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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