📄 sched_setscheduler.html

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>sched_setscheduler</title></head><body bgcolor=white><center><font size=2>The Single UNIX &reg; Specification, Version 2<br>Copyright &copy; 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_008_225">&nbsp;</a>NAME</h4><blockquote>sched_setscheduler - set scheduling policy and parameters(<b>REALTIME</b>)</blockquote><h4><a name = "tag_000_008_226">&nbsp;</a>SYNOPSIS</h4><blockquote><pre><code>#include &lt;<a href="sched.h.html">sched.h</a>&gt;int sched_setscheduler(pid_t <i>pid</i>, int <i>policy</i>,    const struct sched_param *<i>param</i>);</code></pre></blockquote><h4><a name = "tag_000_008_227">&nbsp;</a>DESCRIPTION</h4><blockquote>The<i>sched_setscheduler()</i>function sets the scheduling policy and scheduling parameters ofthe process specified by<i>pid</i>to<i>policy</i>and the parameters specified in the<b>sched_param</b>structure pointed to by<i>param</i>,respectively.The value of the<i>sched_priority</i>member in the<b>sched_param</b>structure is any integer within the inclusive priority rangefor the scheduling policy specified by<i>policy</i>.If the value of<i>pid</i>is negative, the behaviour of the<i>sched_setscheduler()</i>function is unspecified.<p>The possible values for the<i>policy</i>parameter are defined in the header file<i><a href="sched.h.html">&lt;sched.h&gt;</a></i>.<p>If a process specified by<i>pid</i>exists and if the calling process has permission,the scheduling policy and scheduling parameters will be set for theprocess whose process ID is equal to<i>pid</i>.<p>If<i>pid</i>is zero, the scheduling policy and scheduling parameters will be setfor the calling process.<p>The conditions under which one process has the appropriate privilegeto change the scheduling parameters of another processare implementation-dependent.<p>Implementations may require thatthe requesting process have permissionto set its own scheduling parameters or those of another process.Additionally, implementation-dependent restrictions may applyas to the appropriate privilegesrequired to set a process's own scheduling policy, or anotherprocess's scheduling policy, to a particular value.<p>The<i>sched_setscheduler()</i>function is considered successful if it succeedsin setting the scheduling policy and scheduling parameters of the processspecified by<i>pid</i>to the values specified by<i>policy</i>and the structure pointed to by<i>param</i>,respectively.<p>The effect of this function on individual threads is dependent on thescheduling contention scope of the threads:<ul><p><li>For threads with system scheduling contention scope, these functionshave no effect on their scheduling.<p><li>For threads with process scheduling contention scope,&nbsp;the threads' scheduling policy and associated parameterswill not be affected.However,the scheduling of these threads with respect to threads inother processes may be dependent on the scheduling parameters of theirprocess, which are governed using these functions.<p></ul><p>If an implementation supports a two-level scheduling model in whichlibrary threads are multiplexed on top of several kernel scheduledentities, then the underlying kernel scheduled entities for the systemcontention scope threads will not be affected by these functions.<p>The underlying kernel scheduled entities for the process contentionscope threads will have their schedulingpolicy and associated scheduling parameterschanged to the values specified in <i>policy</i> and <i>param</i>, respectively.Kernel scheduled entities for use by process contention scopethreads that are created after this call completesinherit their scheduling policy and associatedscheduling parameters from the process.<p>This function is not atomic with respect to other threads in theprocess.Threads are allowed to continue to executewhile this function call is in the process of changing the scheduling policy and associated scheduling parameters for the underlying kernel scheduled entities used by the process contention scope threads.</blockquote><h4><a name = "tag_000_008_228">&nbsp;</a>RETURN VALUE</h4><blockquote>Upon successful completion, the function returns the formerscheduling policy of the specified process.If the<i>sched_setscheduler()</i>function fails to complete successfully,the policy and scheduling paramenters remain unchanged, andthe function returns a value of -1 and sets<i>errno</i>to indicate the error.</blockquote><h4><a name = "tag_000_008_229">&nbsp;</a>ERRORS</h4><blockquote>The <i>sched_setscheduler()</i>function will fail if:<dl compact><dt>[EINVAL]<dd>The value of the<i>policy</i>parameter is invalid, or one or more of the parameters contained in<i>param</i>is outside the valid range for the specified scheduling policy.<dt>[ENOSYS]<dd>The function<i>sched_setscheduler()</i>is not supported by this implementation.<dt>[EPERM]<dd>The requesting process does not have permissionto set either or both of the scheduling parameters orthe scheduling policy of the specified process.<dt>[ESRCH]<dd>No process can be found corresponding to that specified by<i>pid</i>.</dl></blockquote><h4><a name = "tag_000_008_230">&nbsp;</a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_008_231">&nbsp;</a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_008_232">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_008_233">&nbsp;</a>SEE ALSO</h4><blockquote><i><a href="sched_getparam.html">sched_getparam()</a></i>,<i><a href="sched_getscheduler.html">sched_getscheduler()</a></i>,<i><a href="sched_setparam.html">sched_setparam()</a></i>,<i><a href="sched.h.html">&lt;sched.h&gt;</a></i>.</blockquote><h4>DERIVATION</h4><blockquote>Derived from the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995)</blockquote><hr size=2 noshade><center><font size=2>UNIX &reg; is a registered Trademark of The Open Group.<br>Copyright &copy; 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>
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