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25.\" $FreeBSD: src/share/man/man3/pthread_rwlock_init.3,v 1.11 2007/10/22 10:08:00 ru Exp $
26.\"
27.Dd February 22, 2018
28.Dt PTHREAD_RWLOCK_INIT 3
29.Os
30.Sh NAME
31.Nm pthread_rwlock_init
32.Nd initialize a read/write lock
33.Sh LIBRARY
34.Lb libpthread
35.Sh SYNOPSIS
36.In pthread.h
37.Ft int
38.Fn pthread_rwlock_init "pthread_rwlock_t * restrict lock" "const pthread_rwlockattr_t * restrict attr"
39.Sh DESCRIPTION
40The
41.Fn pthread_rwlock_init
42function is used to initialize a read/write lock, with attributes
43specified by
44.Fa attr .
45If
46.Fa attr
47is NULL, the default read/write lock attributes are used.
48.Pp
49The results of calling
50.Fn pthread_rwlock_init
51with an already initialized lock are undefined.
52.Sh RETURN VALUES
53If successful, the
54.Fn pthread_rwlock_init
55function will return zero.
56Otherwise an error number will be returned
57to indicate the error.
58.Sh ERRORS
59The
60.Fn pthread_rwlock_init
61function will fail if:
62.Bl -tag -width Er
63.It Bq Er EAGAIN
64The system lacked the necessary resources (other than memory) to
65initialize the lock.
66.It Bq Er ENOMEM
67Insufficient memory exists to initialize the lock.
68.It Bq Er EPERM
69The caller does not have sufficient privilege to perform the
70operation.
71.El
72.Pp
73The
74.Fn pthread_rwlock_init
75function may fail if:
76.Bl -tag -width Er
77.It Bq Er EBUSY
78The system has detected an attempt to re-initialize the object
79referenced by
80.Fa lock ,
81a previously initialized but not yet destroyed read/write lock.
82.It Bq Er EINVAL
83The value specified by
84.Fa attr
85is invalid.
86.El
87.Sh SEE ALSO
88.Xr pthread_rwlockattr_init 3 ,
89.Xr pthread_rwlockattr_setpshared 3 ,
90.Xr pthread_rwlock_destroy 3
91.Sh STANDARDS
92The
93.Fn pthread_rwlock_init
94function is expected to conform to
95.St -susv2 .
96.Sh HISTORY
97The
98.Fn pthread_rwlock_init
99function first appeared in
100.Fx 3.0 .
101.Sh BUGS
102The PTHREAD_PROCESS_SHARED attribute is not supported.
103