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
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_unlock(), or pthread_rwlock_wrlock() is
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.
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.
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