.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "PTHREAD_RWLOCK_DESTROY" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" pthread_rwlock_destroy 
.SH NAME
pthread_rwlock_destroy, pthread_rwlock_init \- destroy and initialize
a read\-write lock object
.SH SYNOPSIS
.LP
\fB#include <pthread.h>
.br
.sp
int pthread_rwlock_destroy(pthread_rwlock_t *\fP\fIrwlock\fP\fB);
.br
int pthread_rwlock_init(pthread_rwlock_t *restrict\fP \fIrwlock\fP\fB,
.br
\ \ \ \ \ \  const pthread_rwlockattr_t *restrict\fP \fIattr\fP\fB);
\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIpthread_rwlock_destroy\fP() function shall destroy the read-write
lock object referenced by \fIrwlock\fP and release
any resources used by the lock. The effect of subsequent use of the
lock is undefined until the lock is reinitialized by another
call to \fIpthread_rwlock_init\fP(). An implementation may cause \fIpthread_rwlock_destroy\fP()
to set the object referenced by
\fIrwlock\fP to an invalid value. Results are undefined if \fIpthread_rwlock_destroy\fP()
is called when any thread holds
\fIrwlock\fP. Attempting to destroy an uninitialized read-write lock
results in undefined behavior.
.LP
The \fIpthread_rwlock_init\fP() function shall allocate any resources
required to use the read-write lock referenced by
\fIrwlock\fP and initializes the lock to an unlocked state with attributes
referenced by \fIattr\fP. If \fIattr\fP is NULL, the
default read-write lock attributes shall be used; the effect is the
same as passing the address of a default read-write lock
attributes object. Once initialized, the lock can be used any number
of times without being reinitialized. Results are undefined if
\fIpthread_rwlock_init\fP() is called specifying an already initialized
read-write lock. Results are undefined if a read-write
lock is used without first being initialized.
.LP
If the \fIpthread_rwlock_init\fP() function fails, \fIrwlock\fP shall
not be initialized and the contents of \fIrwlock\fP are
undefined.
.LP
Only the object referenced by \fIrwlock\fP may be used for performing
synchronization. The result of referring to copies of
that object in calls to \fIpthread_rwlock_destroy\fP(), \fIpthread_rwlock_rdlock\fP(),
\fIpthread_rwlock_timedrdlock\fP(), \fIpthread_rwlock_timedwrlock\fP(),
\fIpthread_rwlock_tryrdlock\fP(), \fIpthread_rwlock_trywrlock\fP(),
\fIpthread_rwlock_unlock\fP(), or \fIpthread_rwlock_wrlock\fP() is
undefined.
.SH RETURN VALUE
.LP
If successful, the \fIpthread_rwlock_destroy\fP() and \fIpthread_rwlock_init\fP()
functions shall return zero; otherwise, an
error number shall be returned to indicate the error.
.LP
The [EBUSY] and [EINVAL] error checks, if implemented, act as if they
were performed immediately at the beginning of processing
for the function and caused an error return prior to modifying the
state of the read-write lock specified by \fIrwlock\fP.
.SH ERRORS
.LP
The \fIpthread_rwlock_destroy\fP() function may fail if:
.TP 7
.B EBUSY
The implementation has detected an attempt to destroy the object referenced
by \fIrwlock\fP while it is locked.
.TP 7
.B EINVAL
The value specified by \fIrwlock\fP is invalid.
.sp
.LP
The \fIpthread_rwlock_init\fP() function shall fail if:
.TP 7
.B EAGAIN
The system lacked the necessary resources (other than memory) to initialize
another read-write lock.
.TP 7
.B ENOMEM
Insufficient memory exists to initialize the read-write lock.
.TP 7
.B EPERM
The caller does not have the privilege to perform the operation.
.sp
.LP
The \fIpthread_rwlock_init\fP() function may fail if:
.TP 7
.B EBUSY
The implementation has detected an attempt to reinitialize the object
referenced by \fIrwlock\fP, a previously initialized but
not yet destroyed read-write lock.
.TP 7
.B EINVAL
The value specified by \fIattr\fP is invalid.
.sp
.LP
These functions shall not return an error code of [EINTR].
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
Applications using these and related read-write lock functions may
be subject to priority inversion, as discussed in the Base
Definitions volume of IEEE\ Std\ 1003.1-2001, Section 3.285, Priority
Inversion.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIpthread_rwlock_rdlock\fP() , \fIpthread_rwlock_timedrdlock\fP()
, \fIpthread_rwlock_timedwrlock\fP() , \fIpthread_rwlock_tryrdlock\fP()
, \fIpthread_rwlock_trywrlock\fP() , \fIpthread_rwlock_unlock\fP()
, \fIpthread_rwlock_wrlock\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
\fI<pthread.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .