171 lines
6.2 KiB
HTML
171 lines
6.2 KiB
HTML
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<title><sched.h></title>
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<basefont size="3"> <a name="<sched.h>"></a> <a name="tag_13_39"></a><!-- <sched.h> -->
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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_13_39_01"></a>NAME</h4>
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<blockquote>sched.h - execution scheduling (<b>REALTIME</b>)</blockquote>
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<h4><a name="tag_13_39_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><tt><sup>[<a href="javascript:open_code('PS')">PS</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <sched.h> <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></div>
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</blockquote>
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<h4><a name="tag_13_39_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i><sched.h></i> header shall define the <b>sched_param</b> structure, which contains the scheduling parameters
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required for implementation of each supported scheduling policy. This structure shall contain at least the following member:</p>
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<pre>
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<tt>int sched_priority </tt> Process execution scheduling priority. <tt>
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</tt>
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</pre>
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<p><sup>[<a href="javascript:open_code('SS')">SS|TSP</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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In addition, if _POSIX_SPORADIC_SERVER or _POSIX_THREAD_SPORADIC_SERVER is defined, the <b>sched_param</b> structure defined in
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<i><sched.h></i> shall contain the following members in addition to those specified above:</p>
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<pre>
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<tt>int sched_ss_low_priority</tt> Low scheduling priority for <tt>
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</tt> sporadic server. <tt>
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struct timespec sched_ss_repl_period </tt> Replenishment period for <tt>
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</tt> sporadic server. <tt>
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struct timespec sched_ss_init_budget </tt> Initial budget for sporadic server. <tt>
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int sched_ss_max_repl </tt> Maximum pending replenishments for <tt>
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</tt> sporadic server. <tt>
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</tt>
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</pre>
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<img src="../images/opt-end.gif" alt="[Option End]" border="0">
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<p>Each process is controlled by an associated scheduling policy and priority. Associated with each policy is a priority range.
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Each policy definition specifies the minimum priority range for that policy. The priority ranges for each policy may overlap the
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priority ranges of other policies.</p>
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<p>Four scheduling policies are defined; others may be defined by the implementation. The four standard policies are indicated by
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the values of the following symbolic constants:</p>
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<dl compact>
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<dt>SCHED_FIFO</dt>
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<dd>First in-first out (FIFO) scheduling policy.</dd>
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<dt>SCHED_RR</dt>
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<dd>Round robin scheduling policy.</dd>
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<dt>SCHED_SPORADIC</dt>
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<dd><sup>[<a href="javascript:open_code('SS')">SS|TSP</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
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"0"> Sporadic server scheduling policy. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
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<dt>SCHED_OTHER</dt>
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<dd>Another scheduling policy.</dd>
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</dl>
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<p>The values of these constants are distinct.</p>
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<p>The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.</p>
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<pre>
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<tt>int sched_get_priority_max(int);
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int sched_get_priority_min(int);
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int sched_getparam(pid_t, struct sched_param *);
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int sched_getscheduler(pid_t);
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int sched_rr_get_interval(pid_t, struct timespec *);
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int sched_setparam(pid_t, const struct sched_param *);
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int sched_setscheduler(pid_t, int, const struct sched_param *);
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int sched_yield(void);
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</tt>
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</pre>
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<p>Inclusion of the <i><sched.h></i> header may make visible all symbols from the <a href=
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"time.h.html"><i><time.h></i></a> header.</p>
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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_13_39_04"></a>APPLICATION USAGE</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_13_39_05"></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_13_39_06"></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_13_39_07"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="time.h.html"><i><time.h></i></a></p>
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</blockquote>
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<h4><a name="tag_13_39_08"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 5. Included for alignment with the POSIX Realtime Extension.</p>
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</blockquote>
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<h4><a name="tag_13_39_09"></a>Issue 6</h4>
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<blockquote>
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<p>The <i><sched.h></i> header is marked as part of the Process Scheduling option.</p>
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<p>Sporadic server members are added to the <b>sched_param</b> structure, and the SCHED_SPORADIC scheduling policy is added for
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alignment with IEEE Std 1003.1d-1999.</p>
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<p>IEEE PASC Interpretation 1003.1 #108 is applied, correcting the <b>sched_param</b> structure whose members
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<i>sched_ss_repl_period</i> and <i>sched_ss_init_budget</i> should be type <b>struct timespec</b> and not <b>timespec</b>.</p>
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<p>Symbols from <a href="../basedefs/time.h.html"><i><time.h></i></a> may be made visible when <i><sched.h></i> is
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included.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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POSIX ® is a registered Trademark of The IEEE.<br>
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