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.Dd October 12, 2021
.Dt PTHREAD_ATTR_AFFINITY_NP 3
.Os
.Sh NAME
.Nm pthread_attr_getaffinity_np ,
.Nm pthread_attr_setaffinity_np
.Nd manage CPU affinity in thread attribute objects
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread_np.h
.Ft int
.Fn pthread_attr_getaffinity_np "const pthread_attr_t *pattr" "size_t cpusetsize" "cpuset_t *cpusetp"
.Ft int
.Fn pthread_attr_setaffinity_np "pthread_attr_t *pattr" "size_t cpusetsize" "const cpuset_t *cpusetp"
.Sh DESCRIPTION
The
.Fn pthread_attr_getaffinity_np
and
.Fn pthread_attr_setaffinity_np
functions allow the manipulation of sets of CPUs available to the specified thread attribute object.
.Pp
Masks of type
.Ft cpuset_t
are composed using the
.Dv CPU_SET
macros.
The kernel tolerates large sets as long as all CPUs specified
in the set exist.
Sets smaller than the kernel uses generate an error on calls to
.Fn pthread_attr_getaffinity_np
even if the result set would fit within the user supplied set.
Calls to
.Fn pthread_attr_setaffinity_np
tolerate small sets with no restrictions.
.Pp
The supplied mask should have a size of
.Fa cpusetsize
bytes.
This size is usually provided by calling
.Li sizeof(cpuset_t)
which is ultimately determined by the value of
.Dv CPU_SETSIZE
as defined in
.In sys/cpuset.h .
.Pp
.Fn pthread_attr_getaffinity_np
retrieves the
mask from the thread attribute object specified by
.Fa pattr ,
and stores it in the space provided by
.Fa cpusetp .
.Pp
.Fn pthread_attr_setaffinity_np
sets the mask for the thread attribute object specified by
.Fa pattr
to the value in
.Fa cpusetp .
.Sh RETURN VALUES
If successful, the
.Fn pthread_attr_getaffinity_np
and
.Fn pthread_attr_setaffinity_np
functions will return zero.
Otherwise an error number will be returned
to indicate the error.
.Sh ERRORS
The
.Fn pthread_attr_getaffinity_np
functions will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa pattr
or the attribute specified by it is
.Dv NULL .
.It Bq Er ERANGE
The
.Fa cpusetsize
is too small.
.El
.Pp
The
.Fn pthread_attr_setaffinity_np
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa pattr
or the attribute specified by it is
.Dv NULL .
.It Bq Er EINVAL
The
.Fa cpusetp
specified a CPU that was outside the set supported by the kernel.
.It Bq Er ERANGE
The
.Fa cpusetsize
is too small.
.It Bq Er ENOMEM
Insufficient memory exists to store the cpuset mask.
.El
.Sh SEE ALSO
.Xr cpuset 1 ,
.Xr cpuset 2 ,
.Xr cpuset_getid 2 ,
.Xr cpuset_setid 2 ,
.Xr pthread_getaffinity_np 3 ,
.Xr pthread_np 3 ,
.Xr pthread_setaffinity_np 3
.Sh STANDARDS
The
.Nm pthread_attr_getaffinity_np
and
.Nm pthread_attr_setaffinity_np
functions are non-standard
.Fx
extensions and may be not available on other operating systems.
.Sh HISTORY
The
.Nm pthread_attr_getaffinity_np
and
.Nm pthread_attr_setaffinity_np
functions first appeared in
.Fx 7.2 .
.Sh AUTHORS
.An -nosplit
The
.Nm pthread_attr_getaffinity_np
and
.Nm pthread_attr_setaffinity_np
functions were written by
.An David Xu Aq Mt davidxu@FreeBSD.org ,
and this manpage was written by
.An Xin LI Aq Mt delphij@FreeBSD.org .