]>
Commit | Line | Data |
---|---|---|
3802a3d3 | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
b408026b | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
b408026b LP |
4 | |
5 | <!-- | |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
b975b0d5 | 8 | Copyright 2014 Lennart Poettering |
b408026b LP |
9 | --> |
10 | ||
dc83f27a | 11 | <refentry id="sd_event_add_time" xmlns:xi="http://www.w3.org/2001/XInclude"> |
b408026b LP |
12 | |
13 | <refentryinfo> | |
14 | <title>sd_event_add_time</title> | |
15 | <productname>systemd</productname> | |
16 | ||
17 | <authorgroup> | |
18 | <author> | |
19 | <contrib>Developer</contrib> | |
20 | <firstname>Lennart</firstname> | |
21 | <surname>Poettering</surname> | |
22 | <email>lennart@poettering.net</email> | |
23 | </author> | |
24 | </authorgroup> | |
25 | </refentryinfo> | |
26 | ||
27 | <refmeta> | |
28 | <refentrytitle>sd_event_add_time</refentrytitle> | |
29 | <manvolnum>3</manvolnum> | |
30 | </refmeta> | |
31 | ||
32 | <refnamediv> | |
33 | <refname>sd_event_add_time</refname> | |
34 | <refname>sd_event_source_get_time</refname> | |
35 | <refname>sd_event_source_set_time</refname> | |
36 | <refname>sd_event_source_get_time_accuracy</refname> | |
37 | <refname>sd_event_source_set_time_accuracy</refname> | |
38 | <refname>sd_event_source_get_time_clock</refname> | |
dc83f27a | 39 | <refname>sd_event_time_handler_t</refname> |
b408026b LP |
40 | |
41 | <refpurpose>Add a timer event source to an event loop</refpurpose> | |
42 | </refnamediv> | |
43 | ||
44 | <refsynopsisdiv> | |
45 | <funcsynopsis> | |
dc83f27a LP |
46 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> |
47 | ||
48 | <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo> | |
49 | ||
50 | <funcprototype> | |
51 | <funcdef>typedef int (*<function>sd_event_time_handler_t</function>)</funcdef> | |
52 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
53 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
54 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
55 | </funcprototype> | |
b408026b LP |
56 | |
57 | <funcprototype> | |
58 | <funcdef>int <function>sd_event_add_time</function></funcdef> | |
59 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
60 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
61 | <paramdef>clockid_t <parameter>clock</parameter></paramdef> | |
62 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
63 | <paramdef>uint64_t <parameter>accuracy</parameter></paramdef> | |
64 | <paramdef>sd_event_time_handler_t <parameter>handler</parameter></paramdef> | |
3b3d7d06 | 65 | <paramdef>void *<parameter>userdata</parameter></paramdef> |
b408026b LP |
66 | </funcprototype> |
67 | ||
68 | <funcprototype> | |
69 | <funcdef>int <function>sd_event_source_get_time</function></funcdef> | |
70 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 71 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> |
b408026b LP |
72 | </funcprototype> |
73 | ||
74 | <funcprototype> | |
75 | <funcdef>int <function>sd_event_source_set_time</function></funcdef> | |
76 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 77 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> |
b408026b LP |
78 | </funcprototype> |
79 | ||
80 | <funcprototype> | |
81 | <funcdef>int <function>sd_event_source_get_time_accuracy</function></funcdef> | |
82 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 83 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> |
b408026b LP |
84 | </funcprototype> |
85 | ||
86 | <funcprototype> | |
87 | <funcdef>int <function>sd_event_source_set_time_accuracy</function></funcdef> | |
88 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 89 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> |
b408026b LP |
90 | </funcprototype> |
91 | ||
92 | <funcprototype> | |
93 | <funcdef>int <function>sd_event_source_get_time_clock</function></funcdef> | |
94 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
95 | <paramdef>clockid_t *<parameter>clock</parameter></paramdef> | |
96 | </funcprototype> | |
97 | ||
98 | </funcsynopsis> | |
99 | </refsynopsisdiv> | |
100 | ||
101 | <refsect1> | |
102 | <title>Description</title> | |
103 | ||
393003e1 LP |
104 | <para><function>sd_event_add_time()</function> adds a new timer event source to an event loop. The event loop |
105 | object is specified in the <parameter>event</parameter> parameter, the event source object is returned in the | |
106 | <parameter>source</parameter> parameter. The <parameter>clock</parameter> parameter takes a clock identifier, one | |
107 | of <constant>CLOCK_REALTIME</constant>, <constant>CLOCK_MONOTONIC</constant>, <constant>CLOCK_BOOTTIME</constant>, | |
108 | <constant>CLOCK_REALTIME_ALARM</constant>, or <constant>CLOCK_BOOTTIME_ALARM</constant>. See | |
109 | <citerefentry><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry> for details | |
110 | regarding the various types of clocks. The <parameter>usec</parameter> parameter specifies the earliest time, in | |
111 | microseconds (µs), relative to the clock's epoch, when the timer shall be triggered. If a time already in the past | |
112 | is specified (including <constant>0</constant>), this timer source "fires" immediately and is ready to be | |
595bfe7d | 113 | dispatched. If the parameter is specified as <constant>UINT64_MAX</constant> the timer event will never elapse, |
393003e1 LP |
114 | which may be used as an alternative to explicitly disabling a timer event source with |
115 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The | |
116 | <parameter>accuracy</parameter> parameter specifies an additional accuracy value in µs specifying how much the | |
117 | timer event may be delayed. Use <constant>0</constant> to select the default accuracy (250ms). Use 1µs for maximum | |
118 | accuracy. Consider specifying 60000000µs (1min) or larger for long-running events that may be delayed | |
119 | substantially. Picking higher accuracy values allows the system to coalesce timer events more aggressively, | |
120 | improving power efficiency. The <parameter>handler</parameter> parameter shall reference a function to call when | |
121 | the timer elapses. The handler function will be passed the <parameter>userdata</parameter> pointer, which may be | |
122 | chosen freely by the caller. The handler is also passed the configured trigger time, even if it is actually called | |
123 | slightly later, subject to the specified accuracy value, the kernel timer slack (see | |
124 | <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>), and additional | |
125 | scheduling latencies. To query the actual time the handler was called use | |
dc83f27a | 126 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> |
3144ebca ZJS |
127 | |
128 | <para>By default, the timer will elapse once | |
129 | (<constant>SD_EVENT_ONESHOT</constant>), but this may be changed | |
130 | with | |
131 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
132 | If the handler function returns a negative error code, it will be | |
dc83f27a LP |
133 | disabled after the invocation, even if the |
134 | <constant>SD_EVENT_ON</constant> mode was requested before. Note | |
135 | that a timer event set to <constant>SD_EVENT_ON</constant> will | |
7f3fdb7f | 136 | fire continuously unless its configured time is updated using |
dc83f27a | 137 | <function>sd_event_source_set_time()</function>. |
b408026b LP |
138 | </para> |
139 | ||
dc83f27a LP |
140 | <para>To destroy an event source object use |
141 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
142 | but note that the event source is only removed from the event loop | |
143 | when all references to the event source are dropped. To make sure | |
f23e83b1 ZJS |
144 | an event source does not fire anymore, even if it is still referenced, |
145 | disable the event source using | |
146 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
147 | with <constant>SD_EVENT_OFF</constant>.</para> | |
dc83f27a | 148 | |
7f3fdb7f | 149 | <para>If the second parameter of |
f23e83b1 ZJS |
150 | <function>sd_event_add_time()</function> is |
151 | <constant>NULL</constant> no reference to the event source object | |
152 | is returned. In this case the event source is considered | |
153 | "floating", and will be destroyed implicitly when the event loop | |
154 | itself is destroyed.</para> | |
dc83f27a LP |
155 | |
156 | <para>If the <parameter>handler</parameter> to | |
f23e83b1 ZJS |
157 | <function>sd_event_add_time()</function> is |
158 | <constant>NULL</constant>, and the event source fires, this will | |
159 | be considered a request to exit the event loop. In this case, the | |
160 | <parameter>userdata</parameter> parameter, cast to an integer, is | |
161 | used for the exit code passed to | |
dc83f27a LP |
162 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> |
163 | ||
164 | <para>Use <constant>CLOCK_BOOTTIME_ALARM</constant> and | |
165 | <constant>CLOCK_REALTIME_ALARM</constant> to define event sources | |
166 | that may wake up the system from suspend.</para> | |
167 | ||
168 | <para>In order to set up relative timers (that is, relative to the | |
169 | current time), retrieve the current time via | |
170 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
f23e83b1 | 171 | add the desired timespan to it, and use the result as |
dc83f27a LP |
172 | the <parameter>usec</parameter> parameter to |
173 | <function>sd_event_add_time()</function>.</para> | |
174 | ||
175 | <para>In order to set up repetitive timers (that is, timers that | |
176 | are triggered in regular intervals), set up the timer normally, | |
177 | for the first invocation. Each time the event handler is invoked, | |
178 | update the timer's trigger time with | |
179 | <citerefentry><refentrytitle>sd_event_source_set_time</refentrytitle><manvolnum>3</manvolnum></citerefentry> for the next timer | |
180 | iteration, and reenable the timer using | |
181 | <function>sd_event_source_set_enabled()</function>. To calculate | |
182 | the next point in time to pass to | |
183 | <function>sd_event_source_set_time()</function>, either use as | |
184 | base the <parameter>usec</parameter> parameter passed to the timer | |
185 | callback, or the timestamp returned by | |
186 | <function>sd_event_now()</function>. In the former case timer | |
187 | events will be regular, while in the latter case the scheduling | |
188 | latency will keep accumulating on the timer.</para> | |
189 | ||
b408026b | 190 | <para><function>sd_event_source_get_time()</function> retrieves |
f23e83b1 | 191 | the configured time value of an event source created |
b408026b LP |
192 | previously with <function>sd_event_add_time()</function>. It takes |
193 | the event source object and a pointer to a variable to store the | |
f23e83b1 | 194 | time in, relative to the selected clock's epoch, in µs.</para> |
b408026b LP |
195 | |
196 | <para><function>sd_event_source_set_time()</function> changes the | |
f23e83b1 ZJS |
197 | time of an event source created previously with |
198 | <function>sd_event_add_time()</function>. It takes the event | |
199 | source object and a time relative to the selected clock's epoch, | |
200 | in µs.</para> | |
b408026b LP |
201 | |
202 | <para><function>sd_event_source_get_time_accuracy()</function> | |
037a3ded | 203 | retrieves the configured accuracy value of an event source |
b408026b LP |
204 | created previously with <function>sd_event_add_time()</function>. It |
205 | takes the event source object and a pointer to a variable to store | |
f23e83b1 | 206 | the accuracy in. The accuracy is specified in µs.</para> |
b408026b LP |
207 | |
208 | <para><function>sd_event_source_set_time_accuracy()</function> | |
209 | changes the configured accuracy of a timer event source created | |
210 | previously with <function>sd_event_add_time()</function>. It takes | |
f23e83b1 | 211 | the event source object and accuracy, in µs.</para> |
b408026b LP |
212 | |
213 | <para><function>sd_event_source_get_time_clock()</function> | |
037a3ded | 214 | retrieves the configured clock of an event source created |
b408026b LP |
215 | previously with <function>sd_event_add_time()</function>. It takes |
216 | the event source object and a pointer to a variable to store the | |
217 | clock identifier in.</para> | |
b408026b LP |
218 | </refsect1> |
219 | ||
220 | <refsect1> | |
221 | <title>Return Value</title> | |
222 | ||
223 | <para>On success, these functions return 0 or a positive | |
224 | integer. On failure, they return a negative errno-style error | |
225 | code. </para> | |
226 | </refsect1> | |
227 | ||
228 | <refsect1> | |
229 | <title>Errors</title> | |
230 | ||
f23e83b1 | 231 | <para>Returned values may indicate the following problems:</para> |
b408026b LP |
232 | |
233 | <variablelist> | |
234 | <varlistentry> | |
8474b70c | 235 | <term><constant>-ENOMEM</constant></term> |
b408026b | 236 | |
3144ebca | 237 | <listitem><para>Not enough memory to allocate an object.</para></listitem> |
b408026b LP |
238 | </varlistentry> |
239 | ||
240 | <varlistentry> | |
8474b70c | 241 | <term><constant>-EINVAL</constant></term> |
b408026b LP |
242 | |
243 | <listitem><para>An invalid argument has been passed.</para></listitem> | |
244 | ||
245 | </varlistentry> | |
246 | ||
247 | <varlistentry> | |
8474b70c | 248 | <term><constant>-ESTALE</constant></term> |
b408026b LP |
249 | |
250 | <listitem><para>The event loop is already terminated.</para></listitem> | |
251 | ||
252 | </varlistentry> | |
253 | ||
254 | <varlistentry> | |
8474b70c | 255 | <term><constant>-ECHILD</constant></term> |
b408026b LP |
256 | |
257 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
258 | ||
259 | </varlistentry> | |
260 | ||
261 | <varlistentry> | |
15411c0c | 262 | <term><constant>-EOPNOTSUPP</constant></term> |
b408026b LP |
263 | |
264 | <listitem><para>The selected clock is not supported by the event loop implementation.</para></listitem> | |
265 | ||
266 | </varlistentry> | |
b408026b | 267 | |
dc83f27a LP |
268 | <varlistentry> |
269 | <term><constant>-EDOM</constant></term> | |
b408026b | 270 | |
dc83f27a LP |
271 | <listitem><para>The passed event source is not a timer event source.</para></listitem> |
272 | </varlistentry> | |
273 | </variablelist> | |
b408026b LP |
274 | </refsect1> |
275 | ||
dc83f27a LP |
276 | <xi:include href="libsystemd-pkgconfig.xml" /> |
277 | ||
b408026b LP |
278 | <refsect1> |
279 | <title>See Also</title> | |
280 | ||
281 | <para> | |
282 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
283 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
284 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
dc83f27a LP |
285 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
286 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
3144ebca | 287 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
edf25737 | 288 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
1eb54dc6 | 289 | <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
4dfefc19 | 290 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
dc83f27a LP |
291 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
292 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
293 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
294 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
295 | <citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
296 | <citerefentry project='man-pages'><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
297 | <citerefentry project='man-pages'><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
b408026b LP |
298 | </para> |
299 | </refsect1> | |
300 | ||
301 | </refentry> |