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PTHREAD_ATTR_SETAFFINITY_NP(3)                                          Linux Programmer's Manual                                         PTHREAD_ATTR_SETAFFINITY_NP(3)

NAME
       pthread_attr_setaffinity_np, pthread_attr_getaffinity_np - set/get CPU affinity attribute in thread attributes object

SYNOPSIS
       #define _GNU_SOURCE             /* See feature_test_macros(7) */
       #include <pthread.h>

       int pthread_attr_setaffinity_np(pthread_attr_t *attr,
                          size_t cpusetsize, const cpu_set_t *cpuset);
       int pthread_attr_getaffinity_np(const pthread_attr_t *attr,
                          size_t cpusetsize, cpu_set_t *cpuset);

       Compile and link with -pthread.

DESCRIPTION
       The  pthread_attr_setaffinity_np()  function  sets  the CPU affinity mask attribute of the thread attributes object referred to by attr to the value specified in
       cpuset.  This attribute determines the CPU affinity mask of a thread created using the thread attributes object attr.

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

       The argument cpusetsize is the length (in bytes) of the buffer pointed to by cpuset.  Typically, this argument would be specified as sizeof(cpu_set_t).

       For  more details on CPU affinity masks, see sched_setaffinity(2).  For a description of a set of macros that can be used to manipulate and inspect CPU sets, see
       CPU_SET(3).

RETURN VALUE
       On success, these functions return 0; on error, they return a nonzero error number.

ERRORS
       EINVAL (pthread_attr_setaffinity_np()) cpuset specified a CPU that was outside the set supported by the kernel.  (The kernel configuration option  CONFIG_NR_CPUS
              defines the range of the set supported by the kernel data type used to represent CPU sets.)

       EINVAL (pthread_attr_getaffinity_np()) A CPU in the affinity mask of the thread attributes object referred to by attr lies outside the range specified by cpuset‐
              size (i.e., cpuset/cpusetsize is too small).

       ENOMEM (pthread_attr_setaffinity_np()) Could not allocate memory.

VERSIONS
       These functions are provided by glibc since version 2.3.4.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                                                                                             │ Attribute     │ Value   │
       ├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │pthread_attr_setaffinity_np(), pthread_attr_getaffinity_np()                                                                          │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO
       These functions are nonstandard GNU extensions; hence the suffix "_np" (nonportable) in the names.

NOTES
       In glibc 2.3.3 only, versions of these functions were provided that did not have a cpusetsize argument.  Instead the CPU set size given to the underlying  system
       calls was always sizeof(cpu_set_t).

SEE ALSO
       sched_setaffinity(2), pthread_attr_init(3), pthread_setaffinity_np(3), cpuset(7), pthreads(7)

Linux                                                                          2021-03-22                                                 PTHREAD_ATTR_SETAFFINITY_NP(3)