PTHREAD_RWLOCK_DESTROY(3)  POSIX Programmer's Manual PTHREAD_RWLOCK_DESTROY(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_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.

       See Section 2.9.9, Synchronization Object Copies and Alternative
       Mappings for further requirements.

       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.1-2017, Section 3.291, 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__rwlock__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.1-2017, Section 3.291, Priority
       Inversion, <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_DESTROY(3)
