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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Xenomai API: Threads scheduling services.</title>
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<h1>Threads scheduling services.<br>
<small>
[<a class="el" href="group__posix__thread.html">Threads management services.</a>]</small>
</h1>
<p>
<div class="dynheader">
Collaboration diagram for Threads scheduling services.:</div>
<div class="dynsection">
<center><table><tr><td><img src="group__posix__sched.png" border="0" alt="" usemap="#group____posix____sched_map">
<map name="group____posix____sched_map">
<area shape="rect" href="group__posix__thread.html" title="Threads management services." alt="" coords="7,6,209,30"></map></td></tr></table></center>
</div>
<hr><a name="_details"></a><h2>Detailed Description</h2>
Thread scheduling services.
<p>
Xenomai POSIX skin supports the scheduling policies SCHED_FIFO, SCHED_RR and SCHED_OTHER.<p>
The SCHED_OTHER policy is mainly useful for user-space non-realtime activities that need to synchronize with real-time activities.<p>
The SCHED_RR policy is only effective if the time base is periodic (i.e. if configured with the compilation constant <em>CONFIG_XENO_OPT_POSIX_PERIOD</em> or the <em>xeno_nucleus</em> module parameter <em>tick_arg</em> set to a non null value). The SCHED_RR round-robin time slice is configured with the <em>xeno_posix</em> module parameter <em>time_slice</em>, as a count of system timer clock ticks.<p>
The SCHED_SPORADIC policy is not supported.<p>
The scheduling policy and priority of a thread is set when creating a thread, by using thread creation attributes (see <a class="el" href="group__posix__threadattr.html#gd437fe8caa3ef9f0cb7d69f6f6479df9" title="Set inheritsched attribute.">pthread_attr_setinheritsched()</a>, <a class="el" href="group__posix__threadattr.html#g79b4c9e71486a87ef3014f1c660b33eb" title="Set schedpolicy attribute.">pthread_attr_setschedpolicy()</a> and <a class="el" href="group__posix__threadattr.html#g7d0bf4f0734aca888f89f7341b1df222" title="Set schedparam attribute.">pthread_attr_setschedparam()</a>), or when the thread is already running by using the service <a class="el" href="group__posix__sched.html#g95276f88e1a2cae7a37f792123a99144" title="Set the scheduling policy and parameters of the specified thread.">pthread_setschedparam()</a>.<p>
<dl class="see" compact><dt><b>See also:</b></dt><dd><a href="http://www.opengroup.org/onlinepubs/000095399/functions/xsh_chap02_08.html#tag_02_08_04">Specification.</a> </dd></dl>
<p>
<table border="0" cellpadding="0" cellspacing="0">
<tr><td></td></tr>
<tr><td colspan="2"><br><h2>Functions</h2></td></tr>
<tr><td class="memItemLeft" nowrap align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="group__posix__sched.html#gf1f370fc36ea6b22ed42b5ee3cf82a81">sched_get_priority_min</a> (int policy)</td></tr>
<tr><td class="mdescLeft"> </td><td class="mdescRight">Get minimum priority of the specified scheduling policy. <a href="#gf1f370fc36ea6b22ed42b5ee3cf82a81"></a><br></td></tr>
<tr><td class="memItemLeft" nowrap align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="group__posix__sched.html#gfaebd1698caeb9b9b9e614ad84edd609">sched_get_priority_max</a> (int policy)</td></tr>
<tr><td class="mdescLeft"> </td><td class="mdescRight">Get maximum priority of the specified scheduling policy. <a href="#gfaebd1698caeb9b9b9e614ad84edd609"></a><br></td></tr>
<tr><td class="memItemLeft" nowrap align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="group__posix__sched.html#gf8bce87eeeae4d7e356b0a2d7ef09082">sched_rr_get_interval</a> (int pid, struct timespec *interval)</td></tr>
<tr><td class="mdescLeft"> </td><td class="mdescRight">Get the round-robin scheduling time slice. <a href="#gf8bce87eeeae4d7e356b0a2d7ef09082"></a><br></td></tr>
<tr><td class="memItemLeft" nowrap align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="group__posix__sched.html#gbe5d6e7c9f3293447657b3a6f7d25282">pthread_getschedparam</a> (pthread_t tid, int *pol, struct sched_param *par)</td></tr>
<tr><td class="mdescLeft"> </td><td class="mdescRight">Get the scheduling policy and parameters of the specified thread. <a href="#gbe5d6e7c9f3293447657b3a6f7d25282"></a><br></td></tr>
<tr><td class="memItemLeft" nowrap align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="group__posix__sched.html#g95276f88e1a2cae7a37f792123a99144">pthread_setschedparam</a> (pthread_t tid, int pol, const struct sched_param *par)</td></tr>
<tr><td class="mdescLeft"> </td><td class="mdescRight">Set the scheduling policy and parameters of the specified thread. <a href="#g95276f88e1a2cae7a37f792123a99144"></a><br></td></tr>
<tr><td class="memItemLeft" nowrap align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="group__posix__sched.html#g357cd4b34c13011749dfffb42b489f09">sched_yield</a> (void)</td></tr>
<tr><td class="mdescLeft"> </td><td class="mdescRight">Yield the processor. <a href="#g357cd4b34c13011749dfffb42b489f09"></a><br></td></tr>
</table>
<hr><h2>Function Documentation</h2>
<a class="anchor" name="gbe5d6e7c9f3293447657b3a6f7d25282"></a><!-- doxytag: member="sched.c::pthread_getschedparam" ref="gbe5d6e7c9f3293447657b3a6f7d25282" args="(pthread_t tid, int *pol, struct sched_param *par)" -->
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<td class="memname">int pthread_getschedparam </td>
<td>(</td>
<td class="paramtype">pthread_t </td>
<td class="paramname"> <em>tid</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int * </td>
<td class="paramname"> <em>pol</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">struct sched_param * </td>
<td class="paramname"> <em>par</em></td><td> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td><td width="100%"></td>
</tr>
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</div>
<div class="memdoc">
<p>
Get the scheduling policy and parameters of the specified thread.
<p>
This service returns, at the addresses <em>pol</em> and <em>par</em>, the current scheduling policy and scheduling parameters (i.e. priority) of the Xenomai POSIX skin thread <em>tid</em>. If this service is called from user-space and <em>tid</em> is not the identifier of a Xenomai POSIX skin thread, this service fallback to Linux regular pthread_getschedparam service.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>tid</em> </td><td>target thread;</td></tr>
<tr><td valign="top"></td><td valign="top"><em>pol</em> </td><td>address where the scheduling policy of <em>tid</em> is stored on success;</td></tr>
<tr><td valign="top"></td><td valign="top"><em>par</em> </td><td>address where the scheduling parameters of <em>tid</em> is stored on success.</td></tr>
</table>
</dl>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>0 on success; <p>
an error number if:<ul>
<li>ESRCH, <em>tid</em> is invalid.</li></ul>
</dd></dl>
<dl class="see" compact><dt><b>See also:</b></dt><dd><a href="http://www.opengroup.org/onlinepubs/000095399/functions/pthread_getschedparam.html">Specification.</a> </dd></dl>
<p>References <a class="el" href="include_2nucleus_2thread_8h-source.html#l00048">XNRRB</a>.</p>
<p>Referenced by <a class="el" href="skins_2posix_2thread_8c-source.html#l00152">pthread_create()</a>.</p>
</div>
</div><p>
<a class="anchor" name="g95276f88e1a2cae7a37f792123a99144"></a><!-- doxytag: member="sched.c::pthread_setschedparam" ref="g95276f88e1a2cae7a37f792123a99144" args="(pthread_t tid, int pol, const struct sched_param *par)" -->
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<td class="memname">int pthread_setschedparam </td>
<td>(</td>
<td class="paramtype">pthread_t </td>
<td class="paramname"> <em>tid</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"> <em>pol</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const struct sched_param * </td>
<td class="paramname"> <em>par</em></td><td> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td><td width="100%"></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>
Set the scheduling policy and parameters of the specified thread.
<p>
This service set the scheduling policy of the Xenomai POSIX skin thread <em>tid</em> to the value <em>pol</em>, and its scheduling parameters (i.e. its priority) to the value pointed to by <em>par</em>.<p>
When used in user-space, passing the current thread ID as <em>tid</em> argument, this service turns the current thread into a Xenomai POSIX skin thread. If <em>tid</em> is neither the identifier of the current thread nor the identifier of a Xenomai POSIX skin thread this service falls back to the regular <a class="el" href="group__posix__sched.html#g95276f88e1a2cae7a37f792123a99144" title="Set the scheduling policy and parameters of the specified thread.">pthread_setschedparam()</a> service, hereby causing the current thread to switch to secondary mode if it is Xenomai thread.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>tid</em> </td><td>target thread;</td></tr>
<tr><td valign="top"></td><td valign="top"><em>pol</em> </td><td>scheduling policy, one of SCHED_FIFO, SCHED_RR or SCHED_OTHER;</td></tr>
<tr><td valign="top"></td><td valign="top"><em>par</em> </td><td>scheduling parameters address.</td></tr>
</table>
</dl>
<dl class="return" compact><dt><b>Returns:</b></dt><dd>0 on success; <p>
an error number if:<ul>
<li>ESRCH, <em>tid</em> is invalid;</li><li>EINVAL, <em>pol</em> or <em>par->sched_priority</em> is invalid;</li><li>EAGAIN, in user-space, insufficient memory exists in the system heap, increase CONFIG_XENO_OPT_SYS_HEAPSZ;</li><li>EFAULT, in user-space, <em>par</em> is an invalid address;</li><li>EPERM, in user-space, the calling process does not have superuser permissions.</li></ul>
</dd></dl>
<dl class="see" compact><dt><b>See also:</b></dt><dd><a href="http://www.opengroup.org/onlinepubs/000095399/functions/pthread_setschedparam.html">Specification.</a> </dd></dl>
<dl compact><dt><b>Examples: </b></dt><dd>
<a class="el" href="rtcan__rtt_8c-example.html#a3">rtcan_rtt.c</a>.</dl>
<p>References <a class="el" href="pod_8c-source.html#l01784">xnpod_renice_thread()</a>, <a class="el" href="pod_8c-source.html#l02377">xnpod_schedule()</a>, <a class="el" href="pod_8c-source.html#l01036">xnpod_set_thread_mode()</a>, and <a class="el" href="include_2nucleus_2thread_8h-source.html#l00048">XNRRB</a>.</p>
</div>
</div><p>
<a class="anchor" name="gfaebd1698caeb9b9b9e614ad84edd609"></a><!-- doxytag: member="sched.c::sched_get_priority_max" ref="gfaebd1698caeb9b9b9e614ad84edd609" args="(int policy)" -->
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<td class="memname">int sched_get_priority_max </td>
<td>(</td>
<td class="paramtype">int </td>
<td class="paramname"> <em>policy</em> </td>
<td> ) </td>
<td width="100%"></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>
Get maximum priority of the specified scheduling policy.
<p>
This service returns the maximum priority of the scheduling policy <em>policy</em>.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>policy</em> </td><td>scheduling policy, one of SCHED_FIFO, SCHED_RR, or SCHED_OTHER.</td></tr>
</table>
</dl>
<dl compact><dt><b>Return values:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>0</em> </td><td>on success; </td></tr>
<tr><td valign="top"></td><td valign="top"><em>-1</em> </td><td>with <em>errno</em> set if:<ul>
<li>EINVAL, <em>policy</em> is invalid.</li></ul>
</td></tr>
</table>
</dl>
<dl class="see" compact><dt><b>See also:</b></dt><dd><a href="http://www.opengroup.org/onlinepubs/000095399/functions/sched_get_priority_max.html">Specification.</a> </dd></dl>
</div>
</div><p>
<a class="anchor" name="gf1f370fc36ea6b22ed42b5ee3cf82a81"></a><!-- doxytag: member="sched.c::sched_get_priority_min" ref="gf1f370fc36ea6b22ed42b5ee3cf82a81" args="(int policy)" -->
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<td class="memname">int sched_get_priority_min </td>
<td>(</td>
<td class="paramtype">int </td>
<td class="paramname"> <em>policy</em> </td>
<td> ) </td>
<td width="100%"></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>
Get minimum priority of the specified scheduling policy.
<p>
This service returns the minimum priority of the scheduling policy <em>policy</em>.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>policy</em> </td><td>scheduling policy, one of SCHED_FIFO, SCHED_RR, or SCHED_OTHER.</td></tr>
</table>
</dl>
<dl compact><dt><b>Return values:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>0</em> </td><td>on success; </td></tr>
<tr><td valign="top"></td><td valign="top"><em>-1</em> </td><td>with <em>errno</em> set if:<ul>
<li>EINVAL, <em>policy</em> is invalid.</li></ul>
</td></tr>
</table>
</dl>
<dl class="see" compact><dt><b>See also:</b></dt><dd><a href="http://www.opengroup.org/onlinepubs/000095399/functions/sched_get_priority_min.html">Specification.</a> </dd></dl>
</div>
</div><p>
<a class="anchor" name="gf8bce87eeeae4d7e356b0a2d7ef09082"></a><!-- doxytag: member="sched.c::sched_rr_get_interval" ref="gf8bce87eeeae4d7e356b0a2d7ef09082" args="(int pid, struct timespec *interval)" -->
<div class="memitem">
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<td class="memname">int sched_rr_get_interval </td>
<td>(</td>
<td class="paramtype">int </td>
<td class="paramname"> <em>pid</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">struct timespec * </td>
<td class="paramname"> <em>interval</em></td><td> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td><td width="100%"></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>
Get the round-robin scheduling time slice.
<p>
This service returns the time quantum used by Xenomai POSIX skin SCHED_RR scheduling policy.<p>
In kernel-space, this service only works if pid is zero, in user-space, round-robin scheduling policy is not supported, and this service not implemented.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>pid</em> </td><td>must be zero;</td></tr>
<tr><td valign="top"></td><td valign="top"><em>interval</em> </td><td>address where the round-robin scheduling time quantum will be returned on success.</td></tr>
</table>
</dl>
<dl compact><dt><b>Return values:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>0</em> </td><td>on success; </td></tr>
<tr><td valign="top"></td><td valign="top"><em>-1</em> </td><td>with <em>errno</em> set if:<ul>
<li>ESRCH, <em>pid</em> is invalid (not 0).</li></ul>
</td></tr>
</table>
</dl>
<dl class="see" compact><dt><b>See also:</b></dt><dd><a href="http://www.opengroup.org/onlinepubs/000095399/functions/sched_rr_get_interval.html">Specification.</a> </dd></dl>
</div>
</div><p>
<a class="anchor" name="g357cd4b34c13011749dfffb42b489f09"></a><!-- doxytag: member="sched.c::sched_yield" ref="g357cd4b34c13011749dfffb42b489f09" args="(void)" -->
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<td class="memname">int sched_yield </td>
<td>(</td>
<td class="paramtype">void </td>
<td class="paramname"> </td>
<td> ) </td>
<td width="100%"></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>
Yield the processor.
<p>
This function move the current thread at the end of its priority group.<p>
<dl compact><dt><b>Return values:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td valign="top"></td><td valign="top"><em>0</em> </td><td></td></tr>
</table>
</dl>
<dl class="see" compact><dt><b>See also:</b></dt><dd><a href="http://www.opengroup.org/onlinepubs/000095399/functions/sched_yield.html">Specification.</a> </dd></dl>
</div>
</div><p>
</div>
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