1.\" $OpenBSD: pthread_rwlock_init.3,v 1.8 2013/06/05 03:44:50 tedu Exp $
2.\" Copyright (c) 1998 Alex Nash
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26.\" $FreeBSD: pthread_rwlock_init.3,v 1.2 1999/08/28 00:03:09 peter Exp $
27.\"
28.Dd $Mdocdate: June 5 2013 $
29.Dt PTHREAD_RWLOCK_INIT 3
30.Os
31.Sh NAME
32.Nm pthread_rwlock_init
33.Nd initialize a read/write lock
34.Sh SYNOPSIS
35.In pthread.h
36.Ft int
37.Fn pthread_rwlock_init "pthread_rwlock_t *lock" "const pthread_rwlockattr_t *attr"
38.Sh DESCRIPTION
39The
40.Fn pthread_rwlock_init
41function is used to initialize a read/write lock, with attributes
42specified by
43.Fa attr .
44If
45.Fa attr
46is NULL, the default read/write lock attributes are used.
47.Pp
48The results of calling
49.Fn pthread_rwlock_init
50with an already initialized lock are undefined.
51.Sh RETURN VALUES
52If successful, the
53.Fn pthread_rwlock_init
54function will return zero.
55Otherwise an error number will be returned to indicate the error.
56.Sh ERRORS
57The
58.Fn pthread_rwlock_init
59function will fail if:
60.Bl -tag -width Er
61.It Bq Er EAGAIN
62The system lacked the necessary resources (other than memory) to
63initialize the lock.
64.It Bq Er ENOMEM
65Insufficient memory exists to initialize the lock.
66.It Bq Er EPERM
67The caller does not have sufficient privilege to perform the
68operation.
69.El
70.Pp
71The
72.Fn pthread_rwlock_init
73function may fail if:
74.Bl -tag -width Er
75.It Bq Er EBUSY
76The system has detected an attempt to re-initialize the object
77referenced by
78.Fa lock ,
79a previously initialized but not yet destroyed read/write lock.
80.It Bq Er EINVAL
81The value specified by
82.Fa attr
83is invalid.
84.El
85.Sh SEE ALSO
86.Xr pthread_rwlock_destroy 3 ,
87.Xr pthread_rwlockattr_init 3 ,
88.Xr pthread_rwlockattr_setpshared 3
89.Sh STANDARDS
90The
91.Fn pthread_rwlock_init
92function is expected to conform to
93.St -susv2 .
94.Sh HISTORY
95The
96.Fn pthread_rwlock_init
97function first appeared in
98.Fx 3.0
99and
100.Ox 2.5 .
101.Sh BUGS
102The PTHREAD_PROCESS_SHARED attribute is not supported.
103