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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"> |
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4 | |
5 | <!-- | |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
b975b0d5 | 8 | This file is part of systemd. |
b408026b | 9 | |
b975b0d5 | 10 | Copyright 2014 Lennart Poettering |
b408026b | 11 | |
b975b0d5 ZJS |
12 | systemd is free software; you can redistribute it and/or modify it |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
b408026b | 16 | |
b975b0d5 ZJS |
17 | systemd is distributed in the hope that it will be useful, but |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
b408026b | 21 | |
b975b0d5 ZJS |
22 | You should have received a copy of the GNU Lesser General Public License |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
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24 | --> |
25 | ||
dc83f27a | 26 | <refentry id="sd_event_add_time" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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27 | |
28 | <refentryinfo> | |
29 | <title>sd_event_add_time</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>Developer</contrib> | |
35 | <firstname>Lennart</firstname> | |
36 | <surname>Poettering</surname> | |
37 | <email>lennart@poettering.net</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>sd_event_add_time</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_event_add_time</refname> | |
49 | <refname>sd_event_source_get_time</refname> | |
50 | <refname>sd_event_source_set_time</refname> | |
51 | <refname>sd_event_source_get_time_accuracy</refname> | |
52 | <refname>sd_event_source_set_time_accuracy</refname> | |
53 | <refname>sd_event_source_get_time_clock</refname> | |
dc83f27a | 54 | <refname>sd_event_time_handler_t</refname> |
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55 | |
56 | <refpurpose>Add a timer event source to an event loop</refpurpose> | |
57 | </refnamediv> | |
58 | ||
59 | <refsynopsisdiv> | |
60 | <funcsynopsis> | |
dc83f27a LP |
61 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> |
62 | ||
63 | <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo> | |
64 | ||
65 | <funcprototype> | |
66 | <funcdef>typedef int (*<function>sd_event_time_handler_t</function>)</funcdef> | |
67 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
68 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
69 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
70 | </funcprototype> | |
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71 | |
72 | <funcprototype> | |
73 | <funcdef>int <function>sd_event_add_time</function></funcdef> | |
74 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
75 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
76 | <paramdef>clockid_t <parameter>clock</parameter></paramdef> | |
77 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
78 | <paramdef>uint64_t <parameter>accuracy</parameter></paramdef> | |
79 | <paramdef>sd_event_time_handler_t <parameter>handler</parameter></paramdef> | |
3b3d7d06 | 80 | <paramdef>void *<parameter>userdata</parameter></paramdef> |
b408026b LP |
81 | </funcprototype> |
82 | ||
83 | <funcprototype> | |
84 | <funcdef>int <function>sd_event_source_get_time</function></funcdef> | |
85 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 86 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> |
b408026b LP |
87 | </funcprototype> |
88 | ||
89 | <funcprototype> | |
90 | <funcdef>int <function>sd_event_source_set_time</function></funcdef> | |
91 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 92 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> |
b408026b LP |
93 | </funcprototype> |
94 | ||
95 | <funcprototype> | |
96 | <funcdef>int <function>sd_event_source_get_time_accuracy</function></funcdef> | |
97 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 98 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> |
b408026b LP |
99 | </funcprototype> |
100 | ||
101 | <funcprototype> | |
102 | <funcdef>int <function>sd_event_source_set_time_accuracy</function></funcdef> | |
103 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 104 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> |
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105 | </funcprototype> |
106 | ||
107 | <funcprototype> | |
108 | <funcdef>int <function>sd_event_source_get_time_clock</function></funcdef> | |
109 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
110 | <paramdef>clockid_t *<parameter>clock</parameter></paramdef> | |
111 | </funcprototype> | |
112 | ||
113 | </funcsynopsis> | |
114 | </refsynopsisdiv> | |
115 | ||
116 | <refsect1> | |
117 | <title>Description</title> | |
118 | ||
393003e1 LP |
119 | <para><function>sd_event_add_time()</function> adds a new timer event source to an event loop. The event loop |
120 | object is specified in the <parameter>event</parameter> parameter, the event source object is returned in the | |
121 | <parameter>source</parameter> parameter. The <parameter>clock</parameter> parameter takes a clock identifier, one | |
122 | of <constant>CLOCK_REALTIME</constant>, <constant>CLOCK_MONOTONIC</constant>, <constant>CLOCK_BOOTTIME</constant>, | |
123 | <constant>CLOCK_REALTIME_ALARM</constant>, or <constant>CLOCK_BOOTTIME_ALARM</constant>. See | |
124 | <citerefentry><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry> for details | |
125 | regarding the various types of clocks. The <parameter>usec</parameter> parameter specifies the earliest time, in | |
126 | microseconds (µs), relative to the clock's epoch, when the timer shall be triggered. If a time already in the past | |
127 | is specified (including <constant>0</constant>), this timer source "fires" immediately and is ready to be | |
595bfe7d | 128 | dispatched. If the parameter is specified as <constant>UINT64_MAX</constant> the timer event will never elapse, |
393003e1 LP |
129 | which may be used as an alternative to explicitly disabling a timer event source with |
130 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The | |
131 | <parameter>accuracy</parameter> parameter specifies an additional accuracy value in µs specifying how much the | |
132 | timer event may be delayed. Use <constant>0</constant> to select the default accuracy (250ms). Use 1µs for maximum | |
133 | accuracy. Consider specifying 60000000µs (1min) or larger for long-running events that may be delayed | |
134 | substantially. Picking higher accuracy values allows the system to coalesce timer events more aggressively, | |
135 | improving power efficiency. The <parameter>handler</parameter> parameter shall reference a function to call when | |
136 | the timer elapses. The handler function will be passed the <parameter>userdata</parameter> pointer, which may be | |
137 | chosen freely by the caller. The handler is also passed the configured trigger time, even if it is actually called | |
138 | slightly later, subject to the specified accuracy value, the kernel timer slack (see | |
139 | <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>), and additional | |
140 | scheduling latencies. To query the actual time the handler was called use | |
dc83f27a | 141 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> |
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142 | |
143 | <para>By default, the timer will elapse once | |
144 | (<constant>SD_EVENT_ONESHOT</constant>), but this may be changed | |
145 | with | |
146 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
147 | If the handler function returns a negative error code, it will be | |
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148 | disabled after the invocation, even if the |
149 | <constant>SD_EVENT_ON</constant> mode was requested before. Note | |
150 | that a timer event set to <constant>SD_EVENT_ON</constant> will | |
7f3fdb7f | 151 | fire continuously unless its configured time is updated using |
dc83f27a | 152 | <function>sd_event_source_set_time()</function>. |
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153 | </para> |
154 | ||
dc83f27a LP |
155 | <para>To destroy an event source object use |
156 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
157 | but note that the event source is only removed from the event loop | |
158 | when all references to the event source are dropped. To make sure | |
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159 | an event source does not fire anymore, even if it is still referenced, |
160 | disable the event source using | |
161 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
162 | with <constant>SD_EVENT_OFF</constant>.</para> | |
dc83f27a | 163 | |
7f3fdb7f | 164 | <para>If the second parameter of |
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165 | <function>sd_event_add_time()</function> is |
166 | <constant>NULL</constant> no reference to the event source object | |
167 | is returned. In this case the event source is considered | |
168 | "floating", and will be destroyed implicitly when the event loop | |
169 | itself is destroyed.</para> | |
dc83f27a LP |
170 | |
171 | <para>If the <parameter>handler</parameter> to | |
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172 | <function>sd_event_add_time()</function> is |
173 | <constant>NULL</constant>, and the event source fires, this will | |
174 | be considered a request to exit the event loop. In this case, the | |
175 | <parameter>userdata</parameter> parameter, cast to an integer, is | |
176 | used for the exit code passed to | |
dc83f27a LP |
177 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> |
178 | ||
179 | <para>Use <constant>CLOCK_BOOTTIME_ALARM</constant> and | |
180 | <constant>CLOCK_REALTIME_ALARM</constant> to define event sources | |
181 | that may wake up the system from suspend.</para> | |
182 | ||
183 | <para>In order to set up relative timers (that is, relative to the | |
184 | current time), retrieve the current time via | |
185 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
f23e83b1 | 186 | add the desired timespan to it, and use the result as |
dc83f27a LP |
187 | the <parameter>usec</parameter> parameter to |
188 | <function>sd_event_add_time()</function>.</para> | |
189 | ||
190 | <para>In order to set up repetitive timers (that is, timers that | |
191 | are triggered in regular intervals), set up the timer normally, | |
192 | for the first invocation. Each time the event handler is invoked, | |
193 | update the timer's trigger time with | |
194 | <citerefentry><refentrytitle>sd_event_source_set_time</refentrytitle><manvolnum>3</manvolnum></citerefentry> for the next timer | |
195 | iteration, and reenable the timer using | |
196 | <function>sd_event_source_set_enabled()</function>. To calculate | |
197 | the next point in time to pass to | |
198 | <function>sd_event_source_set_time()</function>, either use as | |
199 | base the <parameter>usec</parameter> parameter passed to the timer | |
200 | callback, or the timestamp returned by | |
201 | <function>sd_event_now()</function>. In the former case timer | |
202 | events will be regular, while in the latter case the scheduling | |
203 | latency will keep accumulating on the timer.</para> | |
204 | ||
b408026b | 205 | <para><function>sd_event_source_get_time()</function> retrieves |
f23e83b1 | 206 | the configured time value of an event source created |
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207 | previously with <function>sd_event_add_time()</function>. It takes |
208 | the event source object and a pointer to a variable to store the | |
f23e83b1 | 209 | time in, relative to the selected clock's epoch, in µs.</para> |
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210 | |
211 | <para><function>sd_event_source_set_time()</function> changes the | |
f23e83b1 ZJS |
212 | time of an event source created previously with |
213 | <function>sd_event_add_time()</function>. It takes the event | |
214 | source object and a time relative to the selected clock's epoch, | |
215 | in µs.</para> | |
b408026b LP |
216 | |
217 | <para><function>sd_event_source_get_time_accuracy()</function> | |
037a3ded | 218 | retrieves the configured accuracy value of an event source |
b408026b LP |
219 | created previously with <function>sd_event_add_time()</function>. It |
220 | takes the event source object and a pointer to a variable to store | |
f23e83b1 | 221 | the accuracy in. The accuracy is specified in µs.</para> |
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222 | |
223 | <para><function>sd_event_source_set_time_accuracy()</function> | |
224 | changes the configured accuracy of a timer event source created | |
225 | previously with <function>sd_event_add_time()</function>. It takes | |
f23e83b1 | 226 | the event source object and accuracy, in µs.</para> |
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227 | |
228 | <para><function>sd_event_source_get_time_clock()</function> | |
037a3ded | 229 | retrieves the configured clock of an event source created |
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230 | previously with <function>sd_event_add_time()</function>. It takes |
231 | the event source object and a pointer to a variable to store the | |
232 | clock identifier in.</para> | |
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233 | </refsect1> |
234 | ||
235 | <refsect1> | |
236 | <title>Return Value</title> | |
237 | ||
238 | <para>On success, these functions return 0 or a positive | |
239 | integer. On failure, they return a negative errno-style error | |
240 | code. </para> | |
241 | </refsect1> | |
242 | ||
243 | <refsect1> | |
244 | <title>Errors</title> | |
245 | ||
f23e83b1 | 246 | <para>Returned values may indicate the following problems:</para> |
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247 | |
248 | <variablelist> | |
249 | <varlistentry> | |
8474b70c | 250 | <term><constant>-ENOMEM</constant></term> |
b408026b | 251 | |
3144ebca | 252 | <listitem><para>Not enough memory to allocate an object.</para></listitem> |
b408026b LP |
253 | </varlistentry> |
254 | ||
255 | <varlistentry> | |
8474b70c | 256 | <term><constant>-EINVAL</constant></term> |
b408026b LP |
257 | |
258 | <listitem><para>An invalid argument has been passed.</para></listitem> | |
259 | ||
260 | </varlistentry> | |
261 | ||
262 | <varlistentry> | |
8474b70c | 263 | <term><constant>-ESTALE</constant></term> |
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264 | |
265 | <listitem><para>The event loop is already terminated.</para></listitem> | |
266 | ||
267 | </varlistentry> | |
268 | ||
269 | <varlistentry> | |
8474b70c | 270 | <term><constant>-ECHILD</constant></term> |
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271 | |
272 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
273 | ||
274 | </varlistentry> | |
275 | ||
276 | <varlistentry> | |
15411c0c | 277 | <term><constant>-EOPNOTSUPP</constant></term> |
b408026b LP |
278 | |
279 | <listitem><para>The selected clock is not supported by the event loop implementation.</para></listitem> | |
280 | ||
281 | </varlistentry> | |
b408026b | 282 | |
dc83f27a LP |
283 | <varlistentry> |
284 | <term><constant>-EDOM</constant></term> | |
b408026b | 285 | |
dc83f27a LP |
286 | <listitem><para>The passed event source is not a timer event source.</para></listitem> |
287 | </varlistentry> | |
288 | </variablelist> | |
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289 | </refsect1> |
290 | ||
dc83f27a LP |
291 | <xi:include href="libsystemd-pkgconfig.xml" /> |
292 | ||
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293 | <refsect1> |
294 | <title>See Also</title> | |
295 | ||
296 | <para> | |
297 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
298 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
299 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
dc83f27a LP |
300 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
301 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
3144ebca | 302 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
edf25737 | 303 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
4dfefc19 | 304 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
dc83f27a LP |
305 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
306 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
307 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
308 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
309 | <citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
310 | <citerefentry project='man-pages'><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
311 | <citerefentry project='man-pages'><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
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312 | </para> |
313 | </refsect1> | |
314 | ||
315 | </refentry> |