.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "PTHREAD_RWLOCK_UNLOCK" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" pthread_rwlock_unlock 
.SH NAME
pthread_rwlock_unlock \- unlock a read-write lock object
.SH SYNOPSIS
.LP
\fB#include <pthread.h>
.br
.sp
int pthread_rwlock_unlock(pthread_rwlock_t\fP \fI*rwlock\fP\fB); \fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIpthread_rwlock_unlock\fP() function shall release a lock held
on the read-write lock object referenced by \fIrwlock\fP.
Results are undefined if the read-write lock \fIrwlock\fP is not held
by the calling thread.
.LP
If this function is called to release a read lock from the read-write
lock object and there are other read locks currently held
on this read-write lock object, the read-write lock object remains
in the read locked state. If this function releases the last
read lock for this read-write lock object, the read-write lock object
shall be put in the unlocked state with no owners.
.LP
If this function is called to release a write lock for this read-write
lock object, the read-write lock object shall be put in
the unlocked state.
.LP
If there are threads blocked on the lock when it becomes available,
the scheduling policy shall determine which thread(s) shall
acquire the lock.   \ If the Thread Execution Scheduling option is
supported, when threads executing with the
scheduling policies SCHED_FIFO, SCHED_RR, or SCHED_SPORADIC are waiting
on the lock, they shall acquire the lock in priority order
when the lock becomes available. For equal priority threads, write
locks shall take precedence over read locks.  If the Thread Execution
Scheduling option is not supported, it is
implementation-defined whether write locks take precedence over read
locks.
.LP
Results are undefined if any of these functions are called with an
uninitialized read-write lock.
.SH RETURN VALUE
.LP
If successful, the \fIpthread_rwlock_unlock\fP() function shall return
zero; otherwise, an error number shall be returned to
indicate the error.
.SH ERRORS
.LP
The \fIpthread_rwlock_unlock\fP() function may fail if:
.TP 7
.B EINVAL
The value specified by \fIrwlock\fP does not refer to an initialized
read-write lock object.
.TP 7
.B EPERM
The current thread does not hold a lock on the read-write lock.
.sp
.LP
The \fIpthread_rwlock_unlock\fP() function shall not return an error
code of [EINTR].
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\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_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 .