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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>sched_setparam</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="sched_setparam"></a> <a name="tag_03_622"></a><!-- sched_setparam --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_622_01"></a>NAME</h4><blockquote>sched_setparam - set scheduling parameters (<b>REALTIME</b>)</blockquote><h4><a name="tag_03_622_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('PS')">PS</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/sched.h.html">sched.h</a>><br><br> int sched_setparam(pid_t</tt> <i>pid</i><tt>, const struct sched_param *</tt><i>param</i><tt>); <img src="../images/opt-end.gif"alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_622_03"></a>DESCRIPTION</h4><blockquote><p>The <i>sched_setparam</i>() function shall set the scheduling parameters of the process specified by <i>pid</i> to the valuesspecified by the <b>sched_param</b> structure pointed to by <i>param</i>. The value of the <i>sched_priority</i> member in the<b>sched_param</b> structure shall be any integer within the inclusive priority range for the current scheduling policy of theprocess specified by <i>pid</i>. Higher numerical values for the priority represent higher priorities. If the value of <i>pid</i>is negative, the behavior of the <i>sched_setparam</i>() function is unspecified.</p><p>If a process specified by <i>pid</i> exists, and if the calling process has permission, the scheduling parameters shall be setfor the process whose process ID is equal to <i>pid</i>.</p><p>If <i>pid</i> is zero, the scheduling parameters shall be set for the calling process.</p><p>The conditions under which one process has permission to change the scheduling parameters of another process areimplementation-defined.</p><p>Implementations may require the requesting process to have the appropriate privilege to set its own scheduling parameters orthose of another process.</p><p>The target process, whether it is running or not running, shall be moved to the tail of the thread list for its priority.</p><p>If the priority of the process specified by the <i>pid</i> argument is set higher than that of the lowest priority runningprocess and if the specified process is ready to run, the process specified by the <i>pid</i> argument shall preempt a lowestpriority running process. Similarly, if the process calling <i>sched_setparam</i>() sets its own priority lower than that of one ormore other non-empty process lists, then the process that is the head of the highest priority list shall also preempt the callingprocess. Thus, in either case, the originating process might not receive notification of the completion of the requested prioritychange until the higher priority process has executed.</p><p><sup>[<a href="javascript:open_code('SS')">SS</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> Ifthe scheduling policy of the target process is SCHED_SPORADIC, the value specified by the <i>sched_ss_low_priority</i> member ofthe <i>param</i> argument shall be any integer within the inclusive priority range for the sporadic server policy. The<i>sched_ss_repl_period</i> and <i>sched_ss_init_budget</i> members of the <i>param</i> argument shall represent the timeparameters to be used by the sporadic server scheduling policy for the target process. The <i>sched_ss_max_repl</i> member of the<i>param</i> argument shall represent the maximum number of replenishments that are allowed to be pending simultaneously for theprocess scheduled under this scheduling policy.</p><p>The specified <i>sched_ss_repl_period</i> shall be greater than or equal to the specified <i>sched_ss_init_budget</i> for thefunction to succeed; if it is not, then the function shall fail.</p><p>The value of <i>sched_ss_max_repl</i> shall be within the inclusive range [1, {SS_REPL_MAX}] for the function to succeed; ifnot, the function shall fail.</p><p>If the scheduling policy of the target process is either SCHED_FIFO or SCHED_RR, the <i>sched_ss_low_priority</i>,<i>sched_ss_repl_period</i>, and <i>sched_ss_init_budget</i> members of the <i>param</i> argument shall have no effect on thescheduling behavior. If the scheduling policy of this process is not SCHED_FIFO, SCHED_RR, or SCHED_SPORADIC, the effects of thesemembers are implementation-defined; this case includes the SCHED_OTHER policy. <img src="../images/opt-end.gif" alt="[Option End]"border="0"></p><p>If the current scheduling policy for the process specified by <i>pid</i> is not SCHED_FIFO, SCHED_RR, <sup>[<a href="javascript:open_code('SS')">SS</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> orSCHED_SPORADIC, <img src="../images/opt-end.gif" alt="[Option End]" border="0"> the result is implementation-defined; thiscase includes the SCHED_OTHER policy.</p><p>The effect of this function on individual threads is dependent on the scheduling contention scope of the threads:</p><ul><li><p>For threads with system scheduling contention scope, these functions shall have no effect on their scheduling.</p></li><li><p>For threads with process scheduling contention scope, the threads' scheduling parameters shall not be affected. However, thescheduling of these threads with respect to threads in other processes may be dependent on the scheduling parameters of theirprocess, which are governed using these functions.</p></li></ul><p>If an implementation supports a two-level scheduling model in which library threads are multiplexed on top of severalkernel-scheduled entities, then the underlying kernel-scheduled entities for the system contention scope threads shall not beaffected by these functions.</p><p>The underlying kernel-scheduled entities for the process contention scope threads shall have their scheduling parameters changedto the value specified in <i>param</i>. Kernel-scheduled entities for use by process contention scope threads that are createdafter this call completes shall inherit their scheduling policy and associated scheduling parameters from the process.</p><p>This function is not atomic with respect to other threads in the process. Threads may continue to execute while this functioncall is in the process of changing the scheduling policy for the underlying kernel-scheduled entities used by the processcontention scope threads.</p></blockquote><h4><a name="tag_03_622_04"></a>RETURN VALUE</h4><blockquote><p>If successful, the <i>sched_setparam</i>() function shall return zero.</p><p>If the call to <i>sched_setparam</i>() is unsuccessful, the priority shall remain unchanged, and the function shall return avalue of -1 and set <i>errno</i> to indicate the error.</p></blockquote><h4><a name="tag_03_622_05"></a>ERRORS</h4><blockquote><p>The <i>sched_setparam</i>() function shall fail if:</p><dl compact><dt>[EINVAL]</dt><dd>One or more of the requested scheduling parameters is outside the range defined for the scheduling policy of the specified<i>pid</i>.</dd><dt>[EPERM]</dt><dd>The requesting process does not have permission to set the scheduling parameters for the specified process, or does not havethe appropriate privilege to invoke <i>sched_setparam</i>().</dd><dt>[ESRCH]</dt><dd>No process can be found corresponding to that specified by <i>pid</i>.</dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_622_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_622_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_622_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_622_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_622_10"></a>SEE ALSO</h4><blockquote><p><a href="sched_getparam.html"><i>sched_getparam</i>()</a> , <a href="sched_getscheduler.html"><i>sched_getscheduler</i>()</a> ,<a href="sched_setscheduler.html"><i>sched_setscheduler</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001,<a href="../basedefs/sched.h.html"><i><sched.h></i></a></p></blockquote><h4><a name="tag_03_622_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 5. Included for alignment with the POSIX Realtime Extension.</p></blockquote><h4><a name="tag_03_622_12"></a>Issue 6</h4><blockquote><p>The <i>sched_setparam</i>() function is marked as part of the Process Scheduling option.</p><p>The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the ProcessScheduling option.</p><p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p><ul><li><p>In the DESCRIPTION, the effect of this function on a thread's scheduling parameters is added.</p></li><li><p>Sections describing two-level scheduling and atomicity of the function are added.</p></li></ul><p>The SCHED_SPORADIC scheduling policy is added for alignment with IEEE Std 1003.1d-1999.</p><p>IEEE PASC Interpretation 1003.1 #100 is applied.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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