NAME

       pthread_rwlock_unlock - unlock a read-write lock object

SYNOPSIS

       #include <pthread.h>

       int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);

DESCRIPTION

       The  pthread_rwlock_unlock()  function shall release a lock held on the read-write lock object referenced
       by rwlock.  Results are undefined if the read-write lock rwlock is not held by the calling thread.

       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.

       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.

       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.

       Results are undefined if any of these functions are called with an uninitialized read-write lock.

RETURN VALUE

       If successful, the pthread_rwlock_unlock() function shall return zero; otherwise, an error  number  shall
       be returned to indicate the error.

ERRORS

       The pthread_rwlock_unlock() function may fail if:

       EINVAL The value specified by rwlock does not refer to an initialized read-write lock object.

       EPERM  The current thread does not hold a lock on the read-write lock.

       The pthread_rwlock_unlock() function shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       pthread_rwlock_destroy()      ,      pthread_rwlock_rdlock()     ,     pthread_rwlock_timedrdlock()     ,
       pthread_rwlock_timedwrlock()    ,    pthread_rwlock_tryrdlock()    ,     pthread_rwlock_trywrlock()     ,
       pthread_rwlock_wrlock() , the Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h>

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 .

IEEE/The Open Group                                   2003                              PTHREAD_RWLOCK_UNLOCK(P)