.\" Copyright (c) 1998 Alex Nash
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.\" $FreeBSD$
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.Dd August 4, 1998
.Dt PTHREAD_RWLOCK_INIT 3
.Os
.Sh NAME
.Nm pthread_rwlock_init
.Nd initialize a read/write lock
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_rwlock_init "pthread_rwlock_t *lock" "const pthread_rwlockattr_t *attr"
.Sh DESCRIPTION
The
.Fn pthread_rwlock_init
function is used to initialize a read/write lock, with attributes
specified by
.Fa attr .
If
.Fa attr
is NULL, the default read/write lock attributes are used.
.Pp
The results of calling
.Fn pthread_rwlock_init
with an already initialized lock are undefined.
.Sh RETURN VALUES
If successful, the
.Fn pthread_rwlock_init
function will return zero.
Otherwise an error number will be returned
to indicate the error.
.Sh ERRORS
The
.Fn pthread_rwlock_init
function will fail if:
.Bl -tag -width Er
.It Bq Er EAGAIN
The system lacked the necessary resources (other than memory) to
initialize the lock.
.It Bq Er ENOMEM
Insufficient memory exists to initialize the lock.
.It Bq Er EPERM
The caller does not have sufficient privilege to perform the
operation.
.El
.Pp
The
.Fn pthread_rwlock_init
function may fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The system has detected an attempt to re-initialize the object
referenced by
.Fa lock ,
a previously initialized but not yet destroyed read/write lock.
.It Bq Er EINVAL
The value specified by
.Fa attr
is invalid.
.El
.Sh SEE ALSO
.Xr pthread_rwlock_destroy 3 ,
.Xr pthread_rwlockattr_init 3 ,
.Xr pthread_rwlockattr_setpshared 3
.Sh STANDARDS
The
.Fn pthread_rwlock_init
function is expected to conform to
.St -susv2 .
.Sh HISTORY
The
.Fn pthread_rwlock_init
function first appeared in
.Fx 3.0 .
.Sh BUGS
The PTHREAD_PROCESS_SHARED attribute is not supported.