For review: pthread_attr_setaffinity_np.3

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Hi all,

And yet another new pthreads man page looking for reviewers.

Cheers,

Michael

.\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
.\"     <mtk.manpages@xxxxxxxxx>
.\"
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.\" manual page may be incorrect or out-of-date.  The author(s) assume no
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.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
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.TH PTHREAD_ATTR_SETAFFINITY_NP 3 2008-11-05 "Linux" "Linux Programmer's Manual"
.SH NAME
pthread_attr_setaffinity_np, pthread_attr_getaffinity_np \- set/get
CPU affinity of a thread
.SH SYNOPSIS
.nf
.B #define _GNU_SOURCE
.B #include <pthread.h>

.BI "int pthread_attr_setaffinity_np(pthread_attr_t " attr ,
.BI "                   size_t " cpusetsize ", const cpu_set_t *" cpuset );
.BI "int pthread_attr_getaffinity_np(pthread_attr_t " attr ,
.BI "                   size_t " cpusetsize ", cpu_set_t *" cpuset );
.sp
Compile and link with \fI\-pthread\fP.
.SH DESCRIPTION
The
.BR pthread_attr_setaffinity_np ()
sets the CPU affinity mask attribute of the
thread attributes object referred to by
.I attr
to the value specified in
.IR cpuset .
This attribute determines the CPU affinity mask
of a thread created using the thread attributes object
.IR attr .

The
.BR pthread_attr_getaffinity_np ()
returns the CPU affinity mask attribute of the thread attributes object
referred to by
.IR attr
in the buffer pointed to by
.IR cpuset .

The argument
.I cpusetsize
is the length (in bytes) of the buffer pointed to by
.IR cpuset .
Normally this argument would be specified as
.IR sizeof(cpu_set_t) .
The constant
.B CPU_SETSIZE
specifies a value one greater than the
maximum CPU number that can be stored in a CPU set.

For more details on CPU affinity masks,
as well as a description of a set of macros
that can be used to manipulate and inspect CPU sets, see
.BR sched_setaffinity (2)
for details.
.SH RETURN VALUE
On success, these functions return 0;
on error, they return a non-zero error number.
.SH ERRORS
.TP
.B EINVAL
.I attr
or
.I cpuset
is invalid.
.TP
.BR EINVAL
.RB ( pthread_attr_setaffinity_np ())
.I cpuset
specified a CPU that was outside the range
permitted by the kernel data type
.\" cpumask_t
used to represent CPU sets.
.\" The raw sched_getaffinity() system call returns the size (in bytes)
.\" of the cpumask_t type.
This range is determined by the kernel configuration option
.BR CONFIG_NR_CPUS .
.TP
.B EINVAL
.RB ( pthread_getaffinity_np ())
A CPU in the affinity mask of the thread attributes object referred to by
.I attr
lies outside the range specified by
.IR cpusetsize .
.TP
.B ENOMEM
.RB ( pthread_attr_setaffinity_np ())
Could not allocate memory.
.SH VERSIONS
These functions are provided by glibc since version 2.3.4.
.SH CONFORMING TO
These functions are non-standard GNU extensions;
hence the suffix "_np" (non-portable) in the names.
.SH NOTES
In glibc 2.3.3 only,
versions of these functions were provided that did not have a
.I cpusetsize
argument.
Instead the CPU set size given to the underlying system calls was always
.IR sizeof(cpu_set_t) .
.SH SEE ALSO
.BR sched_setaffinity (2),
.BR sched_setscheduler (2),
.BR pthread_attr_init (3),
.BR pthread_setaffinity_np (3),
.BR cpuset (7),
.BR pthreads (7)
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