167 lines
6.6 KiB
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167 lines
6.6 KiB
HTML
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<title>sem_timedwait</title>
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<basefont size="3"> <a name="sem_timedwait"></a> <a name="tag_03_634"></a><!-- sem_timedwait -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_634_01"></a>NAME</h4>
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<blockquote>sem_timedwait - lock a semaphore (<b>ADVANCED REALTIME</b>)</blockquote>
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<h4><a name="tag_03_634_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('SEM TMO')">SEM TMO</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/semaphore.h.html">semaphore.h</a>><br>
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#include <<a href="../basedefs/time.h.html">time.h</a>><br>
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<br>
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int sem_timedwait(sem_t *restrict</tt> <i>sem</i><tt>,<br>
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const struct timespec *restrict</tt> <i>abs_timeout</i><tt>); <img src=
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"../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_634_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>sem_timedwait</i>() function shall lock the semaphore referenced by <i>sem</i> as in the <a href=
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"../functions/sem_wait.html"><i>sem_wait</i>()</a> function. However, if the semaphore cannot be locked without waiting for another
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process or thread to unlock the semaphore by performing a <a href="../functions/sem_post.html"><i>sem_post</i>()</a> function, this
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wait shall be terminated when the specified timeout expires.</p>
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<p>The timeout shall expire when the absolute time specified by <i>abs_timeout</i> passes, as measured by the clock on which
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timeouts are based (that is, when the value of that clock equals or exceeds <i>abs_timeout</i>), or if the absolute time specified
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by <i>abs_timeout</i> has already been passed at the time of the call.</p>
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<p><sup>[<a href="javascript:open_code('TMR')">TMR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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If the Timers option is supported, the timeout shall be based on the CLOCK_REALTIME clock. If the Timers option is not supported,
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the timeout shall be based on the system clock as returned by the <a href="../functions/time.html"><i>time</i>()</a> function. The
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resolution of the timeout shall be the resolution of the clock on which it is based. The <b>timespec</b> data type is defined as a
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structure in the <a href="../basedefs/time.h.html"><i><time.h></i></a> header.</p>
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<p>Under no circumstance shall the function fail with a timeout if the semaphore can be locked immediately. The validity of the
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<i>abs_timeout</i> need not be checked if the semaphore can be locked immediately. <img src="../images/opt-end.gif" alt=
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"[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_03_634_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>The <i>sem_timedwait</i>() function shall return zero if the calling process successfully performed the semaphore lock operation
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on the semaphore designated by <i>sem</i>. If the call was unsuccessful, the state of the semaphore shall be unchanged, and the
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function shall return a value of -1 and set <i>errno</i> to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_634_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>sem_timedwait</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd>The <i>sem</i> argument does not refer to a valid semaphore.</dd>
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<dt>[EINVAL]</dt>
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<dd>The process or thread would have blocked, and the <i>abs_timeout</i> parameter specified a nanoseconds field value less than
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zero or greater than or equal to 1000 million.</dd>
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<dt>[ETIMEDOUT]</dt>
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<dd>The semaphore could not be locked before the specified timeout expired.</dd>
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</dl>
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<p>The <i>sem_timedwait</i>() function may fail if:</p>
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<dl compact>
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<dt>[EDEADLK]</dt>
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<dd>A deadlock condition was detected.</dd>
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<dt>[EINTR]</dt>
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<dd>A signal interrupted this function.</dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_634_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_634_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>Applications using these functions may be subject to priority inversion, as discussed in the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap03.html#tag_03_285">Section 3.285, Priority Inversion</a>.</p>
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<p>The <i>sem_timedwait</i>() function is part of the Semaphores and Timeouts options and need not be provided on all
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implementations.</p>
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</blockquote>
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<h4><a name="tag_03_634_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_634_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_634_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="sem_post.html"><i>sem_post</i>()</a> , <a href="sem_trywait.html"><i>sem_trywait</i>()</a> , <a href=
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"sem_wait.html"><i>sem_wait</i>()</a> , <a href="semctl.html"><i>semctl</i>()</a> , <a href="semget.html"><i>semget</i>()</a> , <a
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href="semop.html"><i>semop</i>()</a> , <a href="time.html"><i>time</i>()</a> , the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/semaphore.h.html"><i><semaphore.h></i></a>, <a href=
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"../basedefs/time.h.html"><i><time.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_634_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 6. Derived from IEEE Std 1003.1d-1999.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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