664 lines
16 KiB
HTML
664 lines
16 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of SCHED_SETATTR</TITLE>
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</HEAD><BODY>
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<H1>SCHED_SETATTR</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2019-03-06<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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sched_setattr, sched_getattr -
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set and get scheduling policy and attributes
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/sched.h">sched.h</A>></B>
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<B>int sched_setattr(pid_t </B><I>pid</I><B>, struct sched_attr *</B><I>attr</I><B>,</B>
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<B> unsigned int </B><I>flags</I><B>);</B>
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<B>int sched_getattr(pid_t </B><I>pid</I><B>, struct sched_attr *</B><I>attr</I><B>,</B>
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<B> unsigned int </B><I>size</I><B>, unsigned int </B><I>flags</I><B>);</B>
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</PRE>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<A NAME="lbAE"> </A>
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<H3>sched_setattr()</H3>
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The
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<B>sched_setattr</B>()
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system call sets the scheduling policy and
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associated attributes for the thread whose ID is specified in
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<I>pid</I>.
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If
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<I>pid</I>
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equals zero,
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the scheduling policy and attributes of the calling thread will be set.
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<P>
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Currently, Linux supports the following "normal"
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(i.e., non-real-time) scheduling policies as values that may be specified in
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<I>policy</I>:
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<DL COMPACT>
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<DT id="1"><B>SCHED_OTHER</B>
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<DD>
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the standard round-robin time-sharing policy;
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<DT id="2"><B>SCHED_BATCH</B>
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<DD>
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for "batch" style execution of processes; and
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<DT id="3"><B>SCHED_IDLE</B>
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<DD>
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for running
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<I>very</I>
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low priority background jobs.
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</DL>
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<P>
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Various "real-time" policies are also supported,
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for special time-critical applications that need precise control over
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the way in which runnable threads are selected for execution.
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For the rules governing when a process may use these policies, see
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<B><A HREF="/cgi-bin/man/man2html?7+sched">sched</A></B>(7).
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The real-time policies that may be specified in
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<I>policy</I>
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are:
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<DL COMPACT>
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<DT id="4"><B>SCHED_FIFO</B>
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<DD>
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a first-in, first-out policy; and
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<DT id="5"><B>SCHED_RR</B>
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<DD>
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a round-robin policy.
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</DL>
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<P>
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Linux also provides the following policy:
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<DL COMPACT>
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<DT id="6"><B>SCHED_DEADLINE</B>
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<DD>
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a deadline scheduling policy; see
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<B><A HREF="/cgi-bin/man/man2html?7+sched">sched</A></B>(7)
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for details.
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</DL>
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<P>
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The
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<I>attr</I>
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argument is a pointer to a structure that defines
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the new scheduling policy and attributes for the specified thread.
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This structure has the following form:
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<P>
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struct sched_attr {
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<BR> u32 size; /* Size of this structure */
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<BR> u32 sched_policy; /* Policy (SCHED_*) */
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<BR> u64 sched_flags; /* Flags */
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<BR> s32 sched_nice; /* Nice value (SCHED_OTHER,
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<BR> SCHED_BATCH) */
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<BR> u32 sched_priority; /* Static priority (SCHED_FIFO,
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<BR> SCHED_RR) */
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<BR> /* Remaining fields are for SCHED_DEADLINE */
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<BR> u64 sched_runtime;
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<BR> u64 sched_deadline;
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<BR> u64 sched_period;
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};
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<P>
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The fields of this structure are as follows:
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<DL COMPACT>
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<DT id="7"><B>size</B>
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<DD>
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This field should be set to the size of the structure in bytes, as in
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<I>sizeof(struct sched_attr)</I>.
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If the provided structure is smaller than the kernel structure,
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any additional fields are assumed to be '0'.
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If the provided structure is larger than the kernel structure,
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the kernel verifies that all additional fields are 0;
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if they are not,
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<B>sched_setattr</B>()
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fails with the error
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<B>E2BIG</B>
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and updates
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<I>size</I>
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to contain the size of the kernel structure.
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<DT id="8"><DD>
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The above behavior when the size of the user-space
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<I>sched_attr</I>
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structure does not match the size of the kernel structure
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allows for future extensibility of the interface.
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Malformed applications that pass oversize structures
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won't break in the future if the size of the kernel
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<I>sched_attr</I>
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structure is increased.
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In the future,
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it could also allow applications that know about a larger user-space
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<I>sched_attr</I>
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structure to determine whether they are running on an older kernel
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that does not support the larger structure.
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<DT id="9"><I>sched_policy</I>
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<DD>
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This field specifies the scheduling policy, as one of the
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<B>SCHED_*</B>
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values listed above.
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<DT id="10"><I>sched_flags</I>
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<DD>
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This field contains zero or more of the following flags
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that are ORed together to control scheduling behavior:
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<DL COMPACT><DT id="11"><DD>
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<DL COMPACT>
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<DT id="12"><B>SCHED_FLAG_RESET_ON_FORK</B>
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<DD>
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Children created by
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<B><A HREF="/cgi-bin/man/man2html?2+fork">fork</A></B>(2)
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do not inherit privileged scheduling policies.
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See
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<B><A HREF="/cgi-bin/man/man2html?7+sched">sched</A></B>(7)
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for details.
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<DT id="13"><B>SCHED_FLAG_RECLAIM</B> (since Linux 4.13)
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<DD>
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This flag allows a
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<B>SCHED_DEADLINE</B>
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thread to reclaim bandwidth unused by other real-time threads.
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<DT id="14"><B>SCHED_FLAG_DL_OVERRUN</B> (since Linux 4.16)
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<DD>
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This flag allows an application to get informed about run-time overruns in
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<B>SCHED_DEADLINE</B>
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threads.
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Such overruns may be caused by (for example) coarse execution time accounting
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or incorrect parameter assignment.
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Notification takes the form of a
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<B>SIGXCPU</B>
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signal which is generated on each overrun.
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<DT id="15"><DD>
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This
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<B>SIGXCPU</B>
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signal is
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<I>process-directed</I>
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(see
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<B><A HREF="/cgi-bin/man/man2html?7+signal">signal</A></B>(7))
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rather than thread-directed.
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This is probably a bug.
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On the one hand,
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<B>sched_setattr</B>()
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is being used to set a per-thread attribute.
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On the other hand, if the process-directed signal is delivered to
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a thread inside the process other than the one that had a run-time overrun,
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the application has no way of knowing which thread overran.
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</DL>
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</DL>
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<DT id="16"><I>sched_nice</I>
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<DD>
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This field specifies the nice value to be set when specifying
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<I>sched_policy</I>
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as
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<B>SCHED_OTHER</B>
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or
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<B>SCHED_BATCH</B>.
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The nice value is a number in the range -20 (high priority)
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to +19 (low priority); see
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<B><A HREF="/cgi-bin/man/man2html?7+sched">sched</A></B>(7).
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<DT id="17"><I>sched_priority</I>
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<DD>
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This field specifies the static priority to be set when specifying
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<I>sched_policy</I>
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as
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<B>SCHED_FIFO</B>
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or
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<B>SCHED_RR</B>.
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The allowed range of priorities for these policies can be determined using
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<B><A HREF="/cgi-bin/man/man2html?2+sched_get_priority_min">sched_get_priority_min</A></B>(2)
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and
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<B><A HREF="/cgi-bin/man/man2html?2+sched_get_priority_max">sched_get_priority_max</A></B>(2).
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For other policies, this field must be specified as 0.
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<DT id="18"><I>sched_runtime</I>
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<DD>
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This field specifies the "Runtime" parameter for deadline scheduling.
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The value is expressed in nanoseconds.
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This field, and the next two fields,
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are used only for
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<B>SCHED_DEADLINE</B>
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scheduling; for further details, see
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<B><A HREF="/cgi-bin/man/man2html?7+sched">sched</A></B>(7).
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<DT id="19"><I>sched_deadline</I>
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<DD>
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This field specifies the "Deadline" parameter for deadline scheduling.
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The value is expressed in nanoseconds.
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<DT id="20"><I>sched_period</I>
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<DD>
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This field specifies the "Period" parameter for deadline scheduling.
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The value is expressed in nanoseconds.
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</DL>
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<P>
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The
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<I>flags</I>
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argument is provided to allow for future extensions to the interface;
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in the current implementation it must be specified as 0.
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<A NAME="lbAF"> </A>
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<H3>sched_getattr()</H3>
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The
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<B>sched_getattr</B>()
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system call fetches the scheduling policy and the
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associated attributes for the thread whose ID is specified in
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<I>pid</I>.
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If
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<I>pid</I>
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equals zero,
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the scheduling policy and attributes of the calling thread
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will be retrieved.
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<P>
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The
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<I>size</I>
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argument should be set to the size of the
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<I>sched_attr</I>
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structure as known to user space.
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The value must be at least as large as the size of the initially published
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<I>sched_attr</I>
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structure, or the call fails with the error
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<B>EINVAL</B>.
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<P>
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The retrieved scheduling attributes are placed in the fields of the
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<I>sched_attr</I>
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structure pointed to by
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<I>attr</I>.
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The kernel sets
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<I>attr.size</I>
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to the size of its
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<I>sched_attr</I>
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structure.
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<P>
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If the caller-provided
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<I>attr</I>
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buffer is larger than the kernel's
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<I>sched_attr</I>
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structure,
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the additional bytes in the user-space structure are not touched.
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If the caller-provided structure is smaller than the kernel
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<I>sched_attr</I>
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structure and the kernel needs to return values outside the provided space,
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<B>sched_getattr</B>()
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fails with the error
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<B>E2BIG</B>.
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As with
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<B>sched_setattr</B>(),
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these semantics allow for future extensibility of the interface.
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<P>
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The
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<I>flags</I>
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argument is provided to allow for future extensions to the interface;
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in the current implementation it must be specified as 0.
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<A NAME="lbAG"> </A>
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<H2>RETURN VALUE</H2>
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On success,
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<B>sched_setattr</B>()
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and
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<B>sched_getattr</B>()
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return 0.
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On error, -1 is returned, and
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<I>errno</I>
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is set to indicate the cause of the error.
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<A NAME="lbAH"> </A>
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<H2>ERRORS</H2>
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<B>sched_getattr</B>()
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and
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<B>sched_setattr</B>()
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can both fail for the following reasons:
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<DL COMPACT>
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<DT id="21"><B>EINVAL</B>
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<DD>
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<I>attr</I>
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is NULL; or
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<I>pid</I>
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is negative; or
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<I>flags</I>
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is not zero.
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<DT id="22"><B>ESRCH</B>
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<DD>
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The thread whose ID is
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<I>pid</I>
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could not be found.
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</DL>
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<P>
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In addition,
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<B>sched_getattr</B>()
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can fail for the following reasons:
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<DL COMPACT>
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<DT id="23"><B>E2BIG</B>
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<DD>
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The buffer specified by
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<I>size</I>
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and
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<I>attr</I>
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is too small.
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<DT id="24"><B>EINVAL</B>
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<DD>
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<I>size</I>
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is invalid; that is, it is smaller than the initial version of the
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<I>sched_attr</I>
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structure (48 bytes) or larger than the system page size.
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</DL>
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<P>
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In addition,
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<B>sched_setattr</B>()
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can fail for the following reasons:
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<DL COMPACT>
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<DT id="25"><B>E2BIG</B>
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<DD>
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The buffer specified by
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<I>size</I>
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and
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<I>attr</I>
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is larger than the kernel structure,
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and one or more of the excess bytes is nonzero.
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<DT id="26"><B>EBUSY</B>
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<DD>
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<B>SCHED_DEADLINE</B>
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admission control failure, see
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<B><A HREF="/cgi-bin/man/man2html?7+sched">sched</A></B>(7).
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<DT id="27"><B>EINVAL</B>
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<DD>
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<I>attr.sched_policy</I>
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is not one of the recognized policies;
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<I>attr.sched_flags</I>
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contains a flag other than
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<B>SCHED_FLAG_RESET_ON_FORK</B>;
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or
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<I>attr.sched_priority</I>
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is invalid; or
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<I>attr.sched_policy</I>
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is
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<B>SCHED_DEADLINE</B>
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and the deadline scheduling parameters in
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<I>attr</I>
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are invalid.
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<DT id="28"><B>EPERM</B>
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<DD>
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The caller does not have appropriate privileges.
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<DT id="29"><B>EPERM</B>
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<DD>
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The CPU affinity mask of the thread specified by
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<I>pid</I>
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does not include all CPUs in the system
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(see
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<B><A HREF="/cgi-bin/man/man2html?2+sched_setaffinity">sched_setaffinity</A></B>(2)).
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</DL>
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<A NAME="lbAI"> </A>
|
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<H2>VERSIONS</H2>
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|
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These system calls first appeared in Linux 3.14.
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|
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<A NAME="lbAJ"> </A>
|
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<H2>CONFORMING TO</H2>
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|
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These system calls are nonstandard Linux extensions.
|
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<A NAME="lbAK"> </A>
|
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<H2>NOTES</H2>
|
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|
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<B>sched_setattr</B>()
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|
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provides a superset of the functionality of
|
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<B><A HREF="/cgi-bin/man/man2html?2+sched_setscheduler">sched_setscheduler</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_setparam">sched_setparam</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+nice">nice</A></B>(2),
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and (other than the ability to set the priority of all processes
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belonging to a specified user or all processes in a specified group)
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<B><A HREF="/cgi-bin/man/man2html?2+setpriority">setpriority</A></B>(2).
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|
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Analogously,
|
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<B>sched_getattr</B>()
|
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provides a superset of the functionality of
|
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<B><A HREF="/cgi-bin/man/man2html?2+sched_getscheduler">sched_getscheduler</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_getparam">sched_getparam</A></B>(2),
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and (partially)
|
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<B><A HREF="/cgi-bin/man/man2html?2+getpriority">getpriority</A></B>(2).
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|
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<A NAME="lbAL"> </A>
|
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<H2>BUGS</H2>
|
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|
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In Linux versions up to
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3.15,
|
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<B>sched_settattr</B>()
|
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failed with the error
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<B>EFAULT</B>
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instead of
|
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<B>E2BIG</B>
|
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|
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for the case described in ERRORS.
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<A NAME="lbAM"> </A>
|
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+chrt">chrt</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?2+nice">nice</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_get_priority_max">sched_get_priority_max</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_get_priority_min">sched_get_priority_min</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_getaffinity">sched_getaffinity</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_getparam">sched_getparam</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_getscheduler">sched_getscheduler</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_rr_get_interval">sched_rr_get_interval</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_setaffinity">sched_setaffinity</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_setparam">sched_setparam</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_setscheduler">sched_setscheduler</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sched_yield">sched_yield</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+setpriority">setpriority</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?3+pthread_getschedparam">pthread_getschedparam</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+pthread_setschedparam">pthread_setschedparam</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+pthread_setschedprio">pthread_setschedprio</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?7+capabilities">capabilities</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?7+cpuset">cpuset</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?7+sched">sched</A></B>(7)
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<A NAME="lbAN"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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|
can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="30"><A HREF="#lbAB">NAME</A><DD>
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<DT id="31"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="32"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DL>
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<DT id="33"><A HREF="#lbAE">sched_setattr()</A><DD>
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<DT id="34"><A HREF="#lbAF">sched_getattr()</A><DD>
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</DL>
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<DT id="35"><A HREF="#lbAG">RETURN VALUE</A><DD>
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<DT id="36"><A HREF="#lbAH">ERRORS</A><DD>
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<DT id="37"><A HREF="#lbAI">VERSIONS</A><DD>
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<DT id="38"><A HREF="#lbAJ">CONFORMING TO</A><DD>
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<DT id="39"><A HREF="#lbAK">NOTES</A><DD>
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<DT id="40"><A HREF="#lbAL">BUGS</A><DD>
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<DT id="41"><A HREF="#lbAM">SEE ALSO</A><DD>
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<DT id="42"><A HREF="#lbAN">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:34 GMT, March 31, 2021
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</BODY>
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</HTML>
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