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33.Dd January 15, 2017
34.Dt PTHREAD_ATTR_SETAFFINITY_NP 2
35.Os
36.Sh NAME
37.Nm pthread_attr_setaffinity_np ,
38.Nm pthread_attr_getaffinity_np
39.Nd set and get the thread's CPU affinity mask attribute
40.Sh LIBRARY
41.Lb libpthread
42.Sh SYNOPSIS
43.In pthread.h
44.In pthread_np.h
45.Ft int
46.Fn pthread_attr_setaffinity_np "pthread_attr_t *attr" "size_t cpusetsize" "const cpu_set_t *mask"
47.Ft int
48.Fn pthread_attr_getaffinity_np "const pthread_attr_t *attr" "size_t cpusetsize" "cpu_set_t *mask"
49.Sh DESCRIPTION
50The
51.Fn pthread_attr_setaffinity_np
52sets the CPU affinity mask of the
53.Fa attr
54to the value specified by the
55.Fa mask .
56The
57.Fa cpusetsize
58is the length (in bytes) of the data pointed to by
59.Fa mask .
60Normally this argument would be specified as sizeof(cpu_set_t).
61The threads created by
62.Xr pthread_create 3
63with the
64.Fa attr
65will use the CPU affinity mask of the
66.Fa attr .
67.Pp
68.Fn pthread_attr_getaffinity_np
69writes the CPU affinity mask of the
70.Fa attr
71to the cpu_set_t structure pointed to by
72.Fa mask .
73.Pp
74The cpu_set_t data structure represents a set of CPUs.
75See
76.Xr sched_setaffinity 2
77for details.
78.Sh RETURN VALUES
79If successful,
80these functions will return zero.
81Otherwise an error number will be returned to indicate the error.
82.Sh ERRORS
83The
84.Fn pthread_attr_setaffinity_np
85and
86.Fn pthread_attr_getaffinity_np
87will fail if:
88.Bl -tag -width Er
89.It Bq Er EFAULT
90The
91.Fa mask
92parameter is outside the process's allocated address space.
93.It Bq Er EINVAL
94The
95.Fa attr
96parameter is invalid.
97.It Bq Er EPERM
98The
99.Fa mask
100does not contain a valid CPU.
101.El
102.Sh SEE ALSO
103.Xr pthread_create 3 ,
104.Xr pthread_getaffinity_np 3 ,
105.Xr pthread_setaffinity_np 3
106.Sh HISTORY
107The
108.Fn pthread_attr_setaffinity_np
109and
110.Fn pthread_attr_getaffinity_np
111functions first appeared in
112.Dx 4.7 .
113