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33.Dd January 14, 2017
34.Dt PTHREAD_SETAFFINITY_NP 2
35.Os
36.Sh NAME
37.Nm pthread_setaffinity_np ,
38.Nm pthread_getaffinity_np
39.Nd set and get the thread's CPU affinity mask
40.Sh LIBRARY
41.Lb libpthread
42.Sh SYNOPSIS
43.In pthread.h
44.In pthread_np.h
45.Ft int
46.Fn pthread_setaffinity_np "pthread_t tid" "size_t cpusetsize" "const cpu_set_t *mask"
47.Ft int
48.Fn pthread_getaffinity_np "pthread_t tid" "size_t cpusetsize" "cpu_set_t *mask"
49.Sh DESCRIPTION
50.Pp
51The
52.Fn pthread_setaffinity_np
53sets the CPU affinity mask of the thread identified by
54.Fa tid
55to the value specified by the
56.Fa mask .
57The
58.Fa cpusetsize
59is the length (in bytes) of the data pointed to by
60.Fa mask .
61Normally this argument would be specified as sizeof(cpu_set_t).
62If the thread specified by the
63.Fa tid
64is the current thread,
65it will be migrated immediately,
66if necessary, otherwise it will be migrated by the scheduler later.
67.Pp
68A process created by
69.Xr fork 2 ,
70.Xr vfork 2 ,
71and
72.Xr rfork 2
73inherits the calling thread's CPU affinity mask.
74Same applies to the threads created by
75.Xr lwp_create 2 ,
76and the threads created by
77.Xr pthread_create 3 .
78.Pp
79.Fn pthread_getaffinity_np
80writes the affinity mask of the thread
81identified by the
82.Fa tid
83to the cpu_set_t structure pointed to by
84.Fa mask .
85.Pp
86The cpu_set_t data structure represents a set of CPUs.
87See
88.Xr sched_setaffinity 2
89for details.
90.Sh RETURN VALUES
91If successful,
92these functions will return zero.
93Otherwise an error number will be returned to indicate the error.
94.Sh ERRORS
95The
96.Fn pthread_setaffinity_np
97and
98.Fn pthread_getaffinity_np
99will fail if:
100.Bl -tag -width Er
101.It Bq Er EFAULT
102The
103.Fa mask
104parameter is outside the process's allocated address space.
105.It Bq Er EINVAL
106The
107.Fa tid
108parameter is invalid.
109.It Bq Er ESRCH
110The thread identified by the
111.Fa tid
112does not exist.
113.It Bq Er EPERM
114The
115.Fa mask
116does not contain a valid CPU.
117.El
118.Sh SEE ALSO
119.Xr fork 2
120.Xr lwp_create 2
121.Xr lwp_getaffinity 2
122.Xr lwp_setaffinity 2
123.Xr pthread_create 3
124.Xr rfork 2
125.Xr sched_getaffinity 2
126.Xr sched_setaffinity 2
127.Xr vfork 2
128.Sh HISTORY
129The
130.Fn pthread_setaffinity_np
131and
132.Fn pthread_getaffinity_np
133functions first appeared in
134.Dx 4.7 .
135