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.Dd March 23, 2010
.Dt PTHREAD_AFFINITY_NP 3
.Os
.Sh NAME
.Nm pthread_getaffinity_np ,
.Nm pthread_setaffinity_np
.Nd manage CPU affinity
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread_np.h
.Ft int
.Fn pthread_getaffinity_np "pthread_t td" "size_t cpusetsize" "cpuset_t *cpusetp"
.Ft int
.Fn pthread_setaffinity_np "pthread_t td" "size_t cpusetsize" "const cpuset_t *cpusetp"
.Sh DESCRIPTION
.Fn pthread_getaffinity_np
and
.Fn pthread_setaffinity_np
allow the manipulation of sets of CPUs available to the specified thread.
.Pp
Masks of type
.Ft cpuset_t
are composed using the
.Xr CPU_SET 3
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_getaffinity_np
even if the result set would fit within the user supplied set.
Calls to
.Fn pthread_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_getaffinity_np
retrieves the
mask from the thread specified by
.Fa td ,
and stores it in the space provided by
.Fa cpusetp .
.Pp
.Fn pthread_setaffinity_np
attempts to set the mask for the thread specified by
.Fa td
to the value in
.Fa cpusetp .
.Sh RETURN VALUES
If successful, the
.Fn pthread_getaffinity_np
and
.Fn pthread_setaffinity_np
functions will return zero.
Otherwise an error number will be returned
to indicate the error.
.Sh ERRORS
The
.Fn pthread_getaffinity_np
and
.Fn pthread_setaffinity_np
functions may fail if:
.Bl -tag -width Er
.It Bq Er EDEADLK
The
.Fn pthread_setaffinity_np
call would leave a thread without a valid CPU to run on because the set
does not overlap with the thread's anonymous mask.
.It Bq Er EFAULT
The
.Fa cpusetp
pointer passed was invalid.
.It Bq Er ESRCH
The thread specified by the
.Fa td
argument could not be found.
.It Bq Er ERANGE
The
.Fa cpusetsize
was either preposterously large or smaller than the kernel set size.
.It Bq Er EPERM
The calling thread did not have the credentials required to complete the
operation.
.El
.Sh SEE ALSO
.Xr cpuset 1 ,
.Xr cpuset 2 ,
.Xr cpuset_getid 2 ,
.Xr cpuset_setid 2 ,
.Xr CPU_SET 3 ,
.Xr pthread 3 ,
.Xr pthread_attr_getaffinity_np 3 ,
.Xr pthread_attr_setaffinity_np 3
.Sh STANDARDS
The
.Nm pthread_getaffinity_np
and
.Nm pthread_setaffinity_np
functions are non-standard
.Fx
extensions and may be not available on other operating systems.
.Sh HISTORY
The
.Nm pthread_getaffinity_np
and
.Nm pthread_setaffinity_np
function first appeared in
.Fx 7.2 .
.Sh AUTHORS
.An -nosplit
The
.Nm pthread_getaffinity_np
and
.Nm pthread_setaffinity_np
functions were written by
.An David Xu
.Aq davidxu@FreeBSD.org ,
and this manpage was written by
.An Xin LI
.Aq delphij@FreeBSD.org .