This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       None.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                         PTHREAD_RWLOCK_UNLOCK(3POSIX)

       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 this function is called with an uninitialized read-write lock.

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

       Thefollowingsectionsareinformative.

       None.

       None.

       pthread_rwlock_unlock — unlock a read-write lock object

       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.

       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.

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

pthread_rwlock_destroy(), pthread_rwlock_rdlock(), pthread_rwlock_timedrdlock(),
       pthread_rwlock_timedwrlock(), pthread_rwlock_trywrlock()

       The Base Definitions volume of POSIX.1‐2017, Section4.12, MemorySynchronization, <pthread.h>

       #include <pthread.h>

       int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);