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PTHREAD_RWLOCK_DESTROY(3P) POSIX Programmer's ManualPTHREAD_RWLOCK_DESTROY(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_destroy, pthread_rwlock_init -- destroy and initialize a
       read-write lock object
SYNOPSIS
       #include <pthread.h>
       int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
       int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock,
           const pthread_rwlockattr_t *restrict attr);
       pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER;
DESCRIPTION
       The pthread_rwlock_destroy() function shall destroy the read-write lock
       object referenced by rwlock and release any resources used by the lock.
       The effect of subsequent use of the lock is undefined until the lock is
       reinitialized by another call to pthread_rwlock_init().  An implementa-
       tion may cause pthread_rwlock_destroy() to set the object referenced by
       rwlock   to   an   invalid   value.   Results    are    undefined    if
       pthread_rwlock_destroy()  is  called  when  any  thread  holds  rwlock.
       Attempting to destroy an uninitialized read-write lock results in unde-
       fined behavior.
       The   pthread_rwlock_init()   function  shall  allocate  any  resources
       required to use the read-write lock referenced by rwlock  and  initial-
       izes  the lock to an unlocked state with attributes referenced by attr.
       If attr is NULL, the default read-write lock attributes shall be  used;
       the  effect  is the same as passing the address of a default read-write
       lock attributes object. Once initialized, the lock can be used any num-
       ber  of  times  without  being  reinitialized. Results are undefined if
       pthread_rwlock_init() is called specifying an already initialized read-
       write  lock. Results are undefined if a read-write lock is used without
       first being initialized.
       If the pthread_rwlock_init() function fails, rwlock shall not  be  ini-
       tialized and the contents of rwlock are undefined.
       Only  the  object  referenced by rwlock may be used for performing syn-
       chronization. The result of referring to copies of that object in calls
       to          pthread_rwlock_destroy(),          pthread_rwlock_rdlock(),
       pthread_rwlock_timedrdlock(),             pthread_rwlock_timedwrlock(),
       pthread_rwlock_tryrdlock(),                 pthread_rwlock_trywrlock(),
       pthread_rwlock_unlock(), or pthread_rwlock_wrlock() is undefined.
       In cases where default read-write lock attributes are appropriate,  the
       macro  PTHREAD_RWLOCK_INITIALIZER  can be used to initialize read-write
       locks. The effect shall be equivalent to dynamic  initialization  by  a
       call  to  pthread_rwlock_init()  with  the  attr parameter specified as
       NULL, except that no error checks are performed.
       The behavior is undefined if the value specified by the  attr  argument
       to  pthread_rwlock_init()  does  not refer to an initialized read-write
       lock attributes object.
RETURN VALUE
       If successful, the pthread_rwlock_destroy()  and  pthread_rwlock_init()
       functions  shall  return  zero;  otherwise,  an  error  number shall be
       returned to indicate the error.
ERRORS
       The pthread_rwlock_init() function shall fail if:
       EAGAIN The system lacked the necessary resources (other than memory) to
              initialize another read-write lock.
       ENOMEM Insufficient memory exists to initialize the read-write lock.
       EPERM  The caller does not have the privilege to perform the operation.
       These functions shall not return an error code of [EINTR].
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       Applications  using  these and related read-write lock functions may be
       subject to priority inversion, as discussed  in  the  Base  Definitions
       volume of POSIX.1-2008, Section 3.287, Priority Inversion.
RATIONALE
       If  an  implementation  detects  that the value specified by the rwlock
       argument to pthread_rwlock_destroy() 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 attr argu-
       ment  to  pthread_rwlockr_init() does not refer to an initialized read-
       write lock attributes 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_destroy() or pthread_rwlock_init() refers to
       a locked read-write lock object, or detects that the value specified by
       the rwlock argument to pthread_rwlock_init() refers to an already  ini-
       tialized  read-write  lock  object, it is recommended that the function
       should fail and report an [EBUSY] error.
FUTURE DIRECTIONS
       None.
SEE ALSO
       pthread_rwlock_rdlock(), pthread_rwlock_timedrdlock(),
       pthread_rwlock_timedwrlock(), pthread_rwlock_trywrlock(),
       pthread_rwlock_unlock()
       The Base Definitions volume of POSIX.1-2008,  Section  3.287,  Priority
       Inversion, <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_DESTROY(3P)