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<H1>PTHREAD_ATTR_SETAFFINITY_NP</H1>
Section: Linux Programmer's Manual (3)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
<A NAME="lbAB">&nbsp;</A>
<H2>NAME</H2>
pthread_attr_setaffinity_np, pthread_attr_getaffinity_np - set/get
CPU affinity attribute in thread attributes object
<A NAME="lbAC">&nbsp;</A>
<H2>SYNOPSIS</H2>
<PRE>
<B>#define _GNU_SOURCE</B> /* See <A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A>(7) */
<B>#include &lt;<A HREF="file:///usr/include/pthread.h">pthread.h</A>&gt;</B>
<B>int pthread_attr_setaffinity_np(pthread_attr_t *</B><I>attr</I><B>,</B>
<B> size_t </B><I>cpusetsize</I><B>, const cpu_set_t *</B><I>cpuset</I><B>);</B>
<B>int pthread_attr_getaffinity_np(const pthread_attr_t *</B><I>attr</I><B>,</B>
<B> size_t </B><I>cpusetsize</I><B>, cpu_set_t *</B><I>cpuset</I><B>);</B>
Compile and link with <I>-pthread</I>.
</PRE>
<A NAME="lbAD">&nbsp;</A>
<H2>DESCRIPTION</H2>
The
<B>pthread_attr_setaffinity_np</B>()
function
sets the CPU affinity mask attribute of the
thread attributes object referred to by
<I>attr</I>
to the value specified in
<I>cpuset</I>.
This attribute determines the CPU affinity mask
of a thread created using the thread attributes object
<I>attr</I>.
<P>
The
<B>pthread_attr_getaffinity_np</B>()
function
returns the CPU affinity mask attribute of the thread attributes object
referred to by
<I>attr</I>
in the buffer pointed to by
<I>cpuset</I>.
<P>
The argument
<I>cpusetsize</I>
is the length (in bytes) of the buffer pointed to by
<I>cpuset</I>.
Typically, this argument would be specified as
<I>sizeof(cpu_set_t)</I>.
<P>
For more details on CPU affinity masks, see
<B><A HREF="/cgi-bin/man/man2html?2+sched_setaffinity">sched_setaffinity</A></B>(2).
For a description of a set of macros
that can be used to manipulate and inspect CPU sets, see
<B><A HREF="/cgi-bin/man/man2html?3+CPU_SET">CPU_SET</A></B>(3).
<A NAME="lbAE">&nbsp;</A>
<H2>RETURN VALUE</H2>
On success, these functions return 0;
on error, they return a nonzero error number.
<A NAME="lbAF">&nbsp;</A>
<H2>ERRORS</H2>
<DL COMPACT>
<DT id="1"><B>EINVAL</B>
<DD>
(<B>pthread_attr_setaffinity_np</B>())
<I>cpuset</I>
specified a CPU that was outside the set supported by the kernel.
(The kernel configuration option
<B>CONFIG_NR_CPUS</B>
defines the range of the set supported by the kernel data type
used to represent CPU sets.)
<DT id="2"><B>EINVAL</B>
<DD>
(<B>pthread_attr_getaffinity_np</B>())
A CPU in the affinity mask of the thread attributes object referred to by
<I>attr</I>
lies outside the range specified by
<I>cpusetsize</I>
(i.e.,
<I>cpuset</I>/<I>cpusetsize</I>
is too small).
<DT id="3"><B>ENOMEM</B>
<DD>
(<B>pthread_attr_setaffinity_np</B>())
Could not allocate memory.
</DL>
<A NAME="lbAG">&nbsp;</A>
<H2>VERSIONS</H2>
These functions are provided by glibc since version 2.3.4.
<A NAME="lbAH">&nbsp;</A>
<H2>ATTRIBUTES</H2>
For an explanation of the terms used in this section, see
<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
<TABLE BORDER>
<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
<TR VALIGN=top><TD>
<B>pthread_attr_setaffinity_np</B>(),
<B>pthread_attr_getaffinity_np</B>()
</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
</TABLE>
<P>
<A NAME="lbAI">&nbsp;</A>
<H2>CONFORMING TO</H2>
These functions are nonstandard GNU extensions;
hence the suffix &quot;_np&quot; (nonportable) in the names.
<A NAME="lbAJ">&nbsp;</A>
<H2>NOTES</H2>
In glibc 2.3.3 only,
versions of these functions were provided that did not have a
<I>cpusetsize</I>
argument.
Instead the CPU set size given to the underlying system calls was always
<I>sizeof(cpu_set_t)</I>.
<A NAME="lbAK">&nbsp;</A>
<H2>SEE ALSO</H2>
<B><A HREF="/cgi-bin/man/man2html?2+sched_setaffinity">sched_setaffinity</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?3+pthread_attr_init">pthread_attr_init</A></B>(3),
<B><A HREF="/cgi-bin/man/man2html?3+pthread_setaffinity_np">pthread_setaffinity_np</A></B>(3),
<B><A HREF="/cgi-bin/man/man2html?7+cpuset">cpuset</A></B>(7),
<B><A HREF="/cgi-bin/man/man2html?7+pthreads">pthreads</A></B>(7)
<A NAME="lbAL">&nbsp;</A>
<H2>COLOPHON</H2>
This page is part of release 5.05 of the Linux
<I>man-pages</I>
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
<P>
<HR>
<A NAME="index">&nbsp;</A><H2>Index</H2>
<DL>
<DT id="4"><A HREF="#lbAB">NAME</A><DD>
<DT id="5"><A HREF="#lbAC">SYNOPSIS</A><DD>
<DT id="6"><A HREF="#lbAD">DESCRIPTION</A><DD>
<DT id="7"><A HREF="#lbAE">RETURN VALUE</A><DD>
<DT id="8"><A HREF="#lbAF">ERRORS</A><DD>
<DT id="9"><A HREF="#lbAG">VERSIONS</A><DD>
<DT id="10"><A HREF="#lbAH">ATTRIBUTES</A><DD>
<DT id="11"><A HREF="#lbAI">CONFORMING TO</A><DD>
<DT id="12"><A HREF="#lbAJ">NOTES</A><DD>
<DT id="13"><A HREF="#lbAK">SEE ALSO</A><DD>
<DT id="14"><A HREF="#lbAL">COLOPHON</A><DD>
</DL>
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Time: 00:05:53 GMT, March 31, 2021
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