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 cpusetsize (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(), │ Thread safety │ MT-Safe │
       │pthread_attr_getaffinity_np()  │               │         │
       └───────────────────────────────┴───────────────┴─────────┘

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)

COLOPHON

       This  page  is  part of release 4.15 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at https://www.kernel.org/doc/man-pages/.