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



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

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.1-2017, Section 4.12, Memory
       Synchronization, <pthread.h>

COPYRIGHT
       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(3)
