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Diffstat (limited to 'man/sd_event_add_time.xml')
| -rw-r--r-- | man/sd_event_add_time.xml | 167 |
1 files changed, 116 insertions, 51 deletions
diff --git a/man/sd_event_add_time.xml b/man/sd_event_add_time.xml index c5f7aee19d..df38f52fc9 100644 --- a/man/sd_event_add_time.xml +++ b/man/sd_event_add_time.xml @@ -21,7 +21,7 @@ along with systemd; If not, see <http://www.gnu.org/licenses/>. --> -<refentry id="sd_event_add_time"> +<refentry id="sd_event_add_time" xmlns:xi="http://www.w3.org/2001/XInclude"> <refentryinfo> <title>sd_event_add_time</title> @@ -49,13 +49,23 @@ <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-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_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> @@ -69,34 +79,27 @@ </funcprototype> <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_source_get_time</function></funcdef> <paramdef>sd_event_source *<parameter>source</parameter></paramdef> - <paramdef>usec_t *<parameter>usec</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>usec_t <parameter>usec</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>usec_t *<parameter>usec</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>usec_t <parameter>usec</parameter></paramdef> + <paramdef>uint64_t <parameter>usec</parameter></paramdef> </funcprototype> <funcprototype> @@ -112,73 +115,130 @@ <title>Description</title> <para><function>sd_event_add_time()</function> adds a new timer - 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>clock</parameter> parameter takes a clock identifier, - one of <constant>CLOCK_REALTIME</constant>, - <constant>CLOCK_MONOTONIC</constant> and + 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 takes a time value in - microseconds, relative to the clock's epoch specifying when the - timer shall elapse the earliest. The + microseconds (µs), relative to the clock's epoch, specifying when + the timer shall elapse the earliest. If a time that already lies + in the past is specified (including 0), the timer source is + dispatched immediately in the next event loop iterations. The <parameter>accuracy</parameter> parameter takes an additional - accuracy value in microseconds specifying a time the timer event - may be delayed. Specify 0 for selecting the default accuracy - (250ms). Specify 1 for most accurate timers. Consider specifying - 60000000 or larger (1h) for long-running events that may be + accuracy value in µs specifying a time the timer event may be + delayed. Specify 0 for selecting the default accuracy + (250ms). Specify 1µs for most accurate timers. Consider specifying + 60000000µs or larger (1min) for long-running events that may be delayed substantially. Picking higher accuracy values allows the system to coalesce timer events more aggressively, thus improving - power efficiency. The <parameter>handler</parameter> shall - reference a function to call when the timer elapses. The handler - function will be passed the <parameter>userdata</parameter> - pointer, which may be chosen freely by the caller. The handler is - also passed the configured time it was triggered, however it might - actually have been called at a slightly later time, subject to the - specified accuracy value, the kernel timer slack (see + power efficiency. The <parameter>handler</parameter> parameter + shall reference a function to call when the timer elapses. The + handler function will be passed the + <parameter>userdata</parameter> pointer, which may be chosen + freely by the caller. The handler is also passed the configured + time it was triggered, however it might actually have been called + at a slightly later time, subject to the specified accuracy value, + the kernel timer slack (see <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>) - and additional scheduling latencies.</para> + and additional scheduling latencies. To query the actual time the + handler was called use + <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</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 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. Note + that a timer event set to <constant>SD_EVENT_ON</constant> will + fire continously unless its configured time is updated using + <function>sd_event_source_set_time()</function>. </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_time()</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>If the <parameter>handler</parameter> to + <function>sd_event_add_time()</function> is passed as NULL, 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 used for the exit code passed 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 sleep to it, and pass 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 a timer 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 - time in microseconds in.</para> + time, relative to the selected clock's epoch, in µs in.</para> <para><function>sd_event_source_set_time()</function> changes the configured time value of a timer event source created previously with <function>sd_event_add_time()</function>. It takes the event source object and a time relative to the selected clock's - epoch, in microseconds.</para> + epoch, in µs.</para> <para><function>sd_event_source_get_time_accuracy()</function> retrieves the configured accuracy value of a timer 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 microseconds in.</para> + the accuracy in µs in.</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 an accuracy, in microseconds.</para> + the event source object and an accuracy, in µs.</para> <para><function>sd_event_source_get_time_clock()</function> retrieves the configured clock of a timer 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> @@ -228,19 +288,17 @@ <listitem><para>The selected clock is not supported by the event loop implementation.</para></listitem> </varlistentry> - </variablelist> - </refsect1> - <refsect1> - <title>Notes</title> + <varlistentry> + <term><constant>-EDOM</constant></term> - <para><function>sd_event_add_time()</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> + <listitem><para>The passed event source is not a timer event source.</para></listitem> + </varlistentry> + </variablelist> </refsect1> + <xi:include href="libsystemd-pkgconfig.xml" /> + <refsect1> <title>See Also</title> @@ -248,11 +306,18 @@ <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_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, - <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</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>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> |