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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 | <!-- | |
b975b0d5 | 6 | This file is part of systemd. |
b408026b | 7 | |
b975b0d5 | 8 | Copyright 2014 Lennart Poettering |
b408026b | 9 | |
b975b0d5 ZJS |
10 | systemd is free software; you can redistribute it and/or modify it |
11 | under the terms of the GNU Lesser General Public License as published by | |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
13 | (at your option) any later version. | |
b408026b | 14 | |
b975b0d5 ZJS |
15 | systemd is distributed in the hope that it will be useful, but |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
18 | Lesser General Public License for more details. | |
b408026b | 19 | |
b975b0d5 ZJS |
20 | You should have received a copy of the GNU Lesser General Public License |
21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
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22 | --> |
23 | ||
dc83f27a | 24 | <refentry id="sd_event_add_time" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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25 | |
26 | <refentryinfo> | |
27 | <title>sd_event_add_time</title> | |
28 | <productname>systemd</productname> | |
29 | ||
30 | <authorgroup> | |
31 | <author> | |
32 | <contrib>Developer</contrib> | |
33 | <firstname>Lennart</firstname> | |
34 | <surname>Poettering</surname> | |
35 | <email>lennart@poettering.net</email> | |
36 | </author> | |
37 | </authorgroup> | |
38 | </refentryinfo> | |
39 | ||
40 | <refmeta> | |
41 | <refentrytitle>sd_event_add_time</refentrytitle> | |
42 | <manvolnum>3</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd_event_add_time</refname> | |
47 | <refname>sd_event_source_get_time</refname> | |
48 | <refname>sd_event_source_set_time</refname> | |
49 | <refname>sd_event_source_get_time_accuracy</refname> | |
50 | <refname>sd_event_source_set_time_accuracy</refname> | |
51 | <refname>sd_event_source_get_time_clock</refname> | |
dc83f27a | 52 | <refname>sd_event_time_handler_t</refname> |
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53 | |
54 | <refpurpose>Add a timer event source to an event loop</refpurpose> | |
55 | </refnamediv> | |
56 | ||
57 | <refsynopsisdiv> | |
58 | <funcsynopsis> | |
dc83f27a LP |
59 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> |
60 | ||
61 | <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo> | |
62 | ||
63 | <funcprototype> | |
64 | <funcdef>typedef int (*<function>sd_event_time_handler_t</function>)</funcdef> | |
65 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
66 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
67 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
68 | </funcprototype> | |
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69 | |
70 | <funcprototype> | |
71 | <funcdef>int <function>sd_event_add_time</function></funcdef> | |
72 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
73 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
74 | <paramdef>clockid_t <parameter>clock</parameter></paramdef> | |
75 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
76 | <paramdef>uint64_t <parameter>accuracy</parameter></paramdef> | |
77 | <paramdef>sd_event_time_handler_t <parameter>handler</parameter></paramdef> | |
3b3d7d06 | 78 | <paramdef>void *<parameter>userdata</parameter></paramdef> |
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79 | </funcprototype> |
80 | ||
81 | <funcprototype> | |
82 | <funcdef>int <function>sd_event_source_get_time</function></funcdef> | |
83 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 84 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> |
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85 | </funcprototype> |
86 | ||
87 | <funcprototype> | |
88 | <funcdef>int <function>sd_event_source_set_time</function></funcdef> | |
89 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 90 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> |
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91 | </funcprototype> |
92 | ||
93 | <funcprototype> | |
94 | <funcdef>int <function>sd_event_source_get_time_accuracy</function></funcdef> | |
95 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 96 | <paramdef>uint64_t *<parameter>usec</parameter></paramdef> |
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97 | </funcprototype> |
98 | ||
99 | <funcprototype> | |
100 | <funcdef>int <function>sd_event_source_set_time_accuracy</function></funcdef> | |
101 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
dc83f27a | 102 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> |
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103 | </funcprototype> |
104 | ||
105 | <funcprototype> | |
106 | <funcdef>int <function>sd_event_source_get_time_clock</function></funcdef> | |
107 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
108 | <paramdef>clockid_t *<parameter>clock</parameter></paramdef> | |
109 | </funcprototype> | |
110 | ||
111 | </funcsynopsis> | |
112 | </refsynopsisdiv> | |
113 | ||
114 | <refsect1> | |
115 | <title>Description</title> | |
116 | ||
117 | <para><function>sd_event_add_time()</function> adds a new timer | |
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118 | event source to an event loop. The event loop object is specified |
119 | in the <parameter>event</parameter> parameter, the event source | |
120 | object is returned in the <parameter>source</parameter> | |
121 | parameter. The <parameter>clock</parameter> parameter takes a | |
122 | clock identifier, one of <constant>CLOCK_REALTIME</constant>, | |
123 | <constant>CLOCK_MONOTONIC</constant>, | |
124 | <constant>CLOCK_BOOTTIME</constant>, | |
125 | <constant>CLOCK_REALTIME_ALARM</constant> or | |
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126 | <constant>CLOCK_BOOTTIME_ALARM</constant>. See |
127 | <citerefentry><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
128 | for details regarding the various types of clocks. The | |
129 | <parameter>usec</parameter> parameter takes a time value in | |
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130 | microseconds (µs), relative to the clock's epoch, specifying when |
131 | the timer shall elapse the earliest. If a time that already lies | |
132 | in the past is specified (including 0), the timer source is | |
133 | dispatched immediately in the next event loop iterations. The | |
b408026b | 134 | <parameter>accuracy</parameter> parameter takes an additional |
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135 | accuracy value in µs specifying a time the timer event may be |
136 | delayed. Specify 0 for selecting the default accuracy | |
137 | (250ms). Specify 1µs for most accurate timers. Consider specifying | |
138 | 60000000µs or larger (1min) for long-running events that may be | |
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139 | delayed substantially. Picking higher accuracy values allows the |
140 | system to coalesce timer events more aggressively, thus improving | |
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141 | power efficiency. The <parameter>handler</parameter> parameter |
142 | shall reference a function to call when the timer elapses. The | |
143 | handler function will be passed the | |
144 | <parameter>userdata</parameter> pointer, which may be chosen | |
145 | freely by the caller. The handler is also passed the configured | |
146 | time it was triggered, however it might actually have been called | |
147 | at a slightly later time, subject to the specified accuracy value, | |
148 | the kernel timer slack (see | |
b408026b | 149 | <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>) |
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150 | and additional scheduling latencies. To query the actual time the |
151 | handler was called use | |
152 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
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153 | |
154 | <para>By default, the timer will elapse once | |
155 | (<constant>SD_EVENT_ONESHOT</constant>), but this may be changed | |
156 | with | |
157 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
158 | If the handler function returns a negative error code, it will be | |
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159 | disabled after the invocation, even if the |
160 | <constant>SD_EVENT_ON</constant> mode was requested before. Note | |
161 | that a timer event set to <constant>SD_EVENT_ON</constant> will | |
7f3fdb7f | 162 | fire continuously unless its configured time is updated using |
dc83f27a | 163 | <function>sd_event_source_set_time()</function>. |
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164 | </para> |
165 | ||
dc83f27a LP |
166 | <para>To destroy an event source object use |
167 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
168 | but note that the event source is only removed from the event loop | |
169 | when all references to the event source are dropped. To make sure | |
170 | an event source does not fire anymore, even when there's still a | |
171 | reference to it kept, consider setting the event source to | |
172 | <constant>SD_EVENT_OFF</constant> with | |
173 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
174 | ||
7f3fdb7f | 175 | <para>If the second parameter of |
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176 | <function>sd_event_add_time()</function> is passed as NULL no |
177 | reference to the event source object is returned. In this case the | |
178 | event source is considered "floating", and will be destroyed | |
179 | implicitly when the event loop itself is destroyed.</para> | |
180 | ||
181 | <para>If the <parameter>handler</parameter> to | |
182 | <function>sd_event_add_time()</function> is passed as NULL, and | |
183 | the event source fires, this will be considered a request to exit | |
184 | the event loop. In this case, the <parameter>userdata</parameter> | |
185 | parameter, cast to an integer is used for the exit code passed to | |
186 | <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
187 | ||
188 | <para>Use <constant>CLOCK_BOOTTIME_ALARM</constant> and | |
189 | <constant>CLOCK_REALTIME_ALARM</constant> to define event sources | |
190 | that may wake up the system from suspend.</para> | |
191 | ||
192 | <para>In order to set up relative timers (that is, relative to the | |
193 | current time), retrieve the current time via | |
194 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
195 | add the desired timespan to sleep to it, and pass the result as | |
196 | the <parameter>usec</parameter> parameter to | |
197 | <function>sd_event_add_time()</function>.</para> | |
198 | ||
199 | <para>In order to set up repetitive timers (that is, timers that | |
200 | are triggered in regular intervals), set up the timer normally, | |
201 | for the first invocation. Each time the event handler is invoked, | |
202 | update the timer's trigger time with | |
203 | <citerefentry><refentrytitle>sd_event_source_set_time</refentrytitle><manvolnum>3</manvolnum></citerefentry> for the next timer | |
204 | iteration, and reenable the timer using | |
205 | <function>sd_event_source_set_enabled()</function>. To calculate | |
206 | the next point in time to pass to | |
207 | <function>sd_event_source_set_time()</function>, either use as | |
208 | base the <parameter>usec</parameter> parameter passed to the timer | |
209 | callback, or the timestamp returned by | |
210 | <function>sd_event_now()</function>. In the former case timer | |
211 | events will be regular, while in the latter case the scheduling | |
212 | latency will keep accumulating on the timer.</para> | |
213 | ||
b408026b LP |
214 | <para><function>sd_event_source_get_time()</function> retrieves |
215 | the configured time value of a timer event source created | |
216 | previously with <function>sd_event_add_time()</function>. It takes | |
217 | the event source object and a pointer to a variable to store the | |
dc83f27a | 218 | time, relative to the selected clock's epoch, in µs in.</para> |
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219 | |
220 | <para><function>sd_event_source_set_time()</function> changes the | |
221 | configured time value of a timer event source created previously | |
222 | with <function>sd_event_add_time()</function>. It takes the event | |
223 | source object and a time relative to the selected clock's | |
dc83f27a | 224 | epoch, in µs.</para> |
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225 | |
226 | <para><function>sd_event_source_get_time_accuracy()</function> | |
227 | retrieves the configured accuracy value of a timer event source | |
228 | created previously with <function>sd_event_add_time()</function>. It | |
229 | takes the event source object and a pointer to a variable to store | |
dc83f27a | 230 | the accuracy in µs in.</para> |
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231 | |
232 | <para><function>sd_event_source_set_time_accuracy()</function> | |
233 | changes the configured accuracy of a timer event source created | |
234 | previously with <function>sd_event_add_time()</function>. It takes | |
dc83f27a | 235 | the event source object and an accuracy, in µs.</para> |
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236 | |
237 | <para><function>sd_event_source_get_time_clock()</function> | |
238 | retrieves the configured clock of a timer event source created | |
239 | previously with <function>sd_event_add_time()</function>. It takes | |
240 | the event source object and a pointer to a variable to store the | |
241 | clock identifier in.</para> | |
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242 | </refsect1> |
243 | ||
244 | <refsect1> | |
245 | <title>Return Value</title> | |
246 | ||
247 | <para>On success, these functions return 0 or a positive | |
248 | integer. On failure, they return a negative errno-style error | |
249 | code. </para> | |
250 | </refsect1> | |
251 | ||
252 | <refsect1> | |
253 | <title>Errors</title> | |
254 | ||
255 | <para>Returned errors may indicate the following problems:</para> | |
256 | ||
257 | <variablelist> | |
258 | <varlistentry> | |
8474b70c | 259 | <term><constant>-ENOMEM</constant></term> |
b408026b | 260 | |
3144ebca | 261 | <listitem><para>Not enough memory to allocate an object.</para></listitem> |
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262 | </varlistentry> |
263 | ||
264 | <varlistentry> | |
8474b70c | 265 | <term><constant>-EINVAL</constant></term> |
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266 | |
267 | <listitem><para>An invalid argument has been passed.</para></listitem> | |
268 | ||
269 | </varlistentry> | |
270 | ||
271 | <varlistentry> | |
8474b70c | 272 | <term><constant>-ESTALE</constant></term> |
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273 | |
274 | <listitem><para>The event loop is already terminated.</para></listitem> | |
275 | ||
276 | </varlistentry> | |
277 | ||
278 | <varlistentry> | |
8474b70c | 279 | <term><constant>-ECHILD</constant></term> |
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280 | |
281 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
282 | ||
283 | </varlistentry> | |
284 | ||
285 | <varlistentry> | |
15411c0c | 286 | <term><constant>-EOPNOTSUPP</constant></term> |
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287 | |
288 | <listitem><para>The selected clock is not supported by the event loop implementation.</para></listitem> | |
289 | ||
290 | </varlistentry> | |
b408026b | 291 | |
dc83f27a LP |
292 | <varlistentry> |
293 | <term><constant>-EDOM</constant></term> | |
b408026b | 294 | |
dc83f27a LP |
295 | <listitem><para>The passed event source is not a timer event source.</para></listitem> |
296 | </varlistentry> | |
297 | </variablelist> | |
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298 | </refsect1> |
299 | ||
dc83f27a LP |
300 | <xi:include href="libsystemd-pkgconfig.xml" /> |
301 | ||
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302 | <refsect1> |
303 | <title>See Also</title> | |
304 | ||
305 | <para> | |
306 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
307 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
308 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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309 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
310 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
3144ebca | 311 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
edf25737 | 312 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
4dfefc19 | 313 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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314 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
315 | <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
316 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
317 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
318 | <citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
319 | <citerefentry project='man-pages'><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>, | |
320 | <citerefentry project='man-pages'><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
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321 | </para> |
322 | </refsect1> | |
323 | ||
324 | </refentry> |