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25.Dd August 17, 2018
26.Dt PTHREAD_RWLOCK_INIT 3
27.Os
28.Sh NAME
29.Nm pthread_rwlock_init
30.Nd initialize a read/write lock
31.Sh LIBRARY
32.Lb libpthread
33.Sh SYNOPSIS
34.In pthread.h
35.Ft int
36.Fn pthread_rwlock_init "pthread_rwlock_t *restrict lock" "const pthread_rwlockattr_t *restrict attr"
37.Sh DESCRIPTION
38The
39.Fn pthread_rwlock_init
40function is used to initialize a read/write lock, with attributes
41specified by
42.Fa attr .
43If
44.Fa attr
45is NULL, the default read/write lock attributes are used.
46.Pp
47The results of calling
48.Fn pthread_rwlock_init
49with an already initialized lock are undefined.
50.Sh RETURN VALUES
51If successful, the
52.Fn pthread_rwlock_init
53function will return zero.
54Otherwise an error number will be returned
55to 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 .
99