Release a previously acquired lock on this mutex.
Declared in <bslmt_recursivemutex.h>
void
unlock();
Release a lock on this object that was previously acquired through a call to lock, or a successful call to tryLock. To fully release the lock, a thread must invoke unlock the same number of times it invoked lock and tryLock. The behavior is undefined unless the calling thread currently owns the lock on this recursive mutex.