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



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 implementa-
       tion-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)