bionic (3) pthread_rwlock_destroy.3posix.gz

Provided by: manpages-posix-dev_2013a-2_all bug

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  implementation  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 undefined behavior.

       The pthread_rwlock_init() function shall allocate any resources  required  to  use  the  read-write  lock
       referenced  by  rwlock  and initializes 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
       number 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 initialized and the contents  of  rwlock
       are undefined.

       Only  the object referenced by rwlock may be used for performing synchronization. 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 argument 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 initialized 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>


       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 .