man3/pthread_attr_setaffinity_np.3

   1 .\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
   2 .\"     <mtk.manpages@gmail.com>
   3 .\"
   4 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   5 .\"
   6 .TH PTHREAD_ATTR_SETAFFINITY_NP 3 2021-03-22 "Linux" "Linux Programmer's Manual"
   7 .SH NAME
   8 pthread_attr_setaffinity_np, pthread_attr_getaffinity_np \- set/get
   9 CPU affinity attribute in thread attributes object
  10 .SH LIBRARY
  11 POSIX threads library
  12 .RI ( libpthread ", " \-lpthread )
  13 .SH SYNOPSIS
  14 .nf
  15 .BR "#define _GNU_SOURCE" "             /* See feature_test_macros(7) */"
  16 .B #include <pthread.h>
  17 .PP
  18 .BI "int pthread_attr_setaffinity_np(pthread_attr_t *" attr ,
  19 .BI "                   size_t " cpusetsize ", const cpu_set_t *" cpuset );
  20 .BI "int pthread_attr_getaffinity_np(const pthread_attr_t *" attr ,
  21 .BI "                   size_t " cpusetsize ", cpu_set_t *" cpuset );
  22 .fi
  23 .SH DESCRIPTION
  24 The
  25 .BR pthread_attr_setaffinity_np ()
  26 function
  27 sets the CPU affinity mask attribute of the
  28 thread attributes object referred to by
  29 .I attr
  30 to the value specified in
  31 .IR cpuset .
  32 This attribute determines the CPU affinity mask
  33 of a thread created using the thread attributes object
  34 .IR attr .
  35 .PP
  36 The
  37 .BR pthread_attr_getaffinity_np ()
  38 function
  39 returns the CPU affinity mask attribute of the thread attributes object
  40 referred to by
  41 .IR attr
  42 in the buffer pointed to by
  43 .IR cpuset .
  44 .PP
  45 The argument
  46 .I cpusetsize
  47 is the length (in bytes) of the buffer pointed to by
  48 .IR cpuset .
  49 Typically, this argument would be specified as
  50 .IR sizeof(cpu_set_t) .
  51 .PP
  52 For more details on CPU affinity masks, see
  53 .BR sched_setaffinity (2).
  54 For a description of a set of macros
  55 that can be used to manipulate and inspect CPU sets, see
  56 .BR CPU_SET (3).
  57 .SH RETURN VALUE
  58 On success, these functions return 0;
  59 on error, they return a nonzero error number.
  60 .SH ERRORS
  61 .TP
  62 .BR EINVAL
  63 .RB ( pthread_attr_setaffinity_np ())
  64 .I cpuset
  65 specified a CPU that was outside the set supported by the kernel.
  66 (The kernel configuration option
  67 .BR CONFIG_NR_CPUS
  68 defines the range of the set supported by the kernel data type
  69 .\" cpumask_t
  70 used to represent CPU sets.)
  71 .\" The raw sched_getaffinity() system call returns the size (in bytes)
  72 .\" of the cpumask_t type.
  73 .TP
  74 .B EINVAL
  75 .RB ( pthread_attr_getaffinity_np ())
  76 A CPU in the affinity mask of the thread attributes object referred to by
  77 .I attr
  78 lies outside the range specified by
  79 .IR cpusetsize
  80 (i.e.,
  81 .IR cpuset / cpusetsize
  82 is too small).
  83 .TP
  84 .B ENOMEM
  85 .RB ( pthread_attr_setaffinity_np ())
  86 Could not allocate memory.
  87 .SH VERSIONS
  88 These functions are provided by glibc since version 2.3.4.
  89 .SH ATTRIBUTES
  90 For an explanation of the terms used in this section, see
  91 .BR attributes (7).
  92 .ad l
  93 .nh
  94 .TS
  95 allbox;
  96 lbx lb lb
  97 l l l.
  98 Interface       Attribute       Value
  99 T{
 100 .BR pthread_attr_setaffinity_np (),
 101 .BR pthread_attr_getaffinity_np ()
 102 T}      Thread safety   MT-Safe
 103 .TE
 104 .hy
 105 .ad
 106 .sp 1
 107 .SH CONFORMING TO
 108 These functions are nonstandard GNU extensions;
 109 hence the suffix "_np" (nonportable) in the names.
 110 .SH NOTES
 111 In glibc 2.3.3 only,
 112 versions of these functions were provided that did not have a
 113 .I cpusetsize
 114 argument.
 115 Instead the CPU set size given to the underlying system calls was always
 116 .IR sizeof(cpu_set_t) .
 117 .SH SEE ALSO
 118 .BR sched_setaffinity (2),
 119 .BR pthread_attr_init (3),
 120 .BR pthread_setaffinity_np (3),
 121 .BR cpuset (7),
 122 .BR pthreads (7)