bionic (3) pthread_rwlock_unlock.3posix.gz

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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 implementation-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_timedrdlock(),
       pthread_rwlock_timedwrlock(), pthread_rwlock_trywrlock()

       The Base Definitions volume of POSIX.1‐2008, Section 4.11, Memory Synchronization, <pthread.h>


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