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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 (consult 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 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 this function is 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 shall not return an error code of
       [EINTR].
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       None.
RATIONALE
       If an implementation detects that the value  specified  by  the  rwlock
       argument  to  pthread_rwlock_unlock()  does not refer to an initialized
       read-write lock object, it is recommended that the function should fail
       and report an [EINVAL] error.
       If  an  implementation  detects  that the value specified by the rwlock
       argument to pthread_rwlock_unlock() refers to a read-write lock  object
       for  which  the  current thread does not hold a lock, it is recommended
       that the function should fail and report an [EPERM] error.
FUTURE DIRECTIONS
       None.
SEE ALSO
       pthread_rwlock_destroy(), pthread_rwlock_rdlock(), pthread_rwlock_time-
       drdlock(), pthread_rwlock_timedwrlock(), pthread_rwlock_trywrlock()
       The  Base Definitions volume of POSIX.1-2008, Section 4.11, Memory Syn-
       chronization, <pthread.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) 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.unix.org/online.html .
       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013            PTHREAD_RWLOCK_UNLOCK(3P)