trusty (3) pthread_rwlock_destroy.3posix.gz

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);

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.

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.

       The  [EBUSY]  and [EINVAL] error checks, if implemented, act as if they were performed immediately at the
       beginning of processing for the function and caused an error return prior to modifying the state  of  the
       read-write lock specified by rwlock.

ERRORS

       The pthread_rwlock_destroy() function may fail if:

       EBUSY  The  implementation has detected an attempt to destroy the object referenced by rwlock while it is
              locked.

       EINVAL The value specified by rwlock is invalid.

       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.

       The pthread_rwlock_init() function may fail if:

       EBUSY  The  implementation  has  detected  an  attempt to reinitialize the object referenced by rwlock, a
              previously initialized but not yet destroyed read-write lock.

       EINVAL The value specified by attr is invalid.

       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 IEEE Std 1003.1-2001, Section 3.285, Priority Inversion.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       pthread_rwlock_rdlock()     ,     pthread_rwlock_timedrdlock()     ,    pthread_rwlock_timedwrlock()    ,
       pthread_rwlock_tryrdlock()     ,     pthread_rwlock_trywrlock()     ,      pthread_rwlock_unlock()      ,
       pthread_rwlock_wrlock() , the Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 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 .