Locks the specified reader-writer lock for writing.
#include <pthread.h>
int pthread_rwlock_wrlock (
pthread_rwlock_t *rwlp);
(IN) Points to the reader-writer lock to lock.
When successful in obtaining the write lock, returns zero.
If no one else has the lock locked for reading or writing, the pthread_rwlock_wrlock function acquires a writing lock for the specified lock. If the lock is not available, the function blocks until a writing lock can be acquired.