Locks

The semantics of a ``lock'' allow the resource to be used by only one thread at a time. The Threads Library supports several types of locks:

• mutual exclusion locks (``mutexes'')

• spin locks

• recursive mutual exclusion locks (``rmutexes'')

• reader-writer locks (these allow non-exclusive access for readers)

A thread that successfully locks a resource is said to ``hold the lock'' or to ``have acquired the lock''. Unlocking is also known as ``releasing the lock''.