PTHREAD_RWLOCK_UNLOCK(3P)                           POSIX Programmer's Manual                          PTHREAD_RWLOCK_UNLOCK(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

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  cur-
       rently 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 schedul-
       ing 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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                     PTHREAD_RWLOCK_UNLOCK(3P)