int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock,
const pthread_rwlockattr_t *restrict attr);
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.
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.
The pthread_rwlock_destroy() function may fail if:
The pthread_rwlock_init() function shall fail if:
The pthread_rwlock_init() function may fail if:
These functions shall not return an error code of [EINTR].
The following sections are informative.
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.
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>